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The measurement of visual impairment in national surveys: a review of available data sources
Prepared for the Thomas Pocklington Trust
The measurement of visual impairment in national surveys:
a review of available data sources
Jo d’Ardenne, Matt Hall, Sally McManus
October 2011
Prepared for the Thomas Pocklington Trust
Contents
Acknowledgements......................................................................................................2
Executive summary .....................................................................2The Pocklington Trust..................................................................................................2Background..................................................................................................................2Aims............................................................................................................................. 2Methodology.................................................................................................................2Notes only:................................................................................................................... 2Results.........................................................................................................................2Discussion....................................................................................................................2Recommendations.......................................................................................................2
1 Background and approach.....................................................21.1 Background.................................................................................................................... 21.1.1 Estimates of the prevalence of visual impairment...........................................................21.1.2 Factors influencing estimates of visual impairment.........................................................21.1.3 Use of general population surveys in estimating prevalence..........................................21.1.4 Variation in the definition of visual impairment................................................................21.2 Aims of this survey review...........................................................................................21.3 Process of review..........................................................................................................21.4 Summary of methodological approach.......................................................................21.5 Consultation with experts.............................................................................................21.6 Report structure............................................................................................................2
2 Types of data collection..........................................................22.1 National surveys of the general population................................................................22.2 National surveys using non-random sampling...........................................................22.3 Regional surveys...........................................................................................................22.4 Surveys of people with visual impairment..................................................................22.5 Surveys of disabled people..........................................................................................22.6 Surveys of other population subgroups......................................................................22.7 Surveys with objective measures................................................................................22.8 Administrative data sources.........................................................................................22.9 Qualitative research with visually impaired people....................................................2
3 Methods....................................................................................23.1 Identification of surveys to include in the analysis....................................................23.1.1 Survey inclusion criteria..................................................................................................23.1.2 Eligible surveys not included in the analysis...................................................................23.1.3 Surveys included in the analysis.....................................................................................23.2 Analysis..........................................................................................................................23.2.1 Statistical approach........................................................................................................23.2.2 Weighting........................................................................................................................ 23.2.3 Missing data................................................................................................................... 2
4 Surveys.....................................................................................2
4.1 Health Survey for England (HSE).................................................................................24.1.1 Visual impairment questions asked................................................................................24.1.2 Long-standing illness code frame...................................................................................24.1.3 Visual impairment prevalence estimates........................................................................24.1.4 Methodological issues....................................................................................................24.1.5 Study contacts and further information...........................................................................24.2 Scottish Health Survey (SHeS).....................................................................................24.2.1 Visual impairment questions asked................................................................................24.2.2 Visual impairment prevalence estimates........................................................................24.2.3 Methodological issues....................................................................................................24.2.4 Study contacts and further information...........................................................................24.3 Welsh Health Survey (WHS) 2007................................................................................24.3.1 Visual impairment questions asked................................................................................24.3.2 Visual impairment prevalence estimates........................................................................24.3.3 Methodological issues....................................................................................................24.3.4 Study contacts and further information...........................................................................24.4 Adult Psychiatric Morbidity Survey (APMS) 2007.......................................................24.4.1 Visual impairment questions asked................................................................................24.4.2 Visual impairment prevalence estimates........................................................................24.4.3 Methodological issues....................................................................................................24.4.4 Study contact and further information.............................................................................24.5 English Longitudinal Study of Aging (ELSA) Wave 4.................................................24.5.1 Visual impairment questions asked................................................................................24.5.2 Visual impairment prevalence estimates........................................................................24.5.3 Methodological issues....................................................................................................24.5.4 Study contacts and further information...........................................................................24.6 Family and Children Survey (FACs) 2006-2007...........................................................24.6.1 Visual impairment questions asked................................................................................24.6.2 Visual impairment prevalence estimates........................................................................24.6.3 Methodological issues....................................................................................................24.6.4 Study contact and further information.............................................................................24.7 Family Resources Survey.............................................................................................24.7.1 Disability questions asked..............................................................................................24.8 FRS Disability Follow-up (1997)...................................................................................24.8.1 Visual impairment questions asked in Disability Follow-Up............................................24.8.2 Visual impairment prevalence estimates........................................................................24.8.3 Methodological issues....................................................................................................24.8.4 Study contact and further information.............................................................................24.9 Living in Wales Survey 2008.........................................................................................24.9.1 Visual impairment questions asked................................................................................24.9.2 Visual impairment prevalence estimates........................................................................24.9.3 Methodological issues....................................................................................................24.9.4 Study contact and further information.............................................................................24.10 Low Income Diet and Nutrition Survey 2005..............................................................24.10.1Visual impairment questions asked................................................................................24.10.2Visual impairment prevalence estimates........................................................................24.10.3Methodological issues....................................................................................................24.10.4Study contacts and further information...........................................................................2
4.11 National Diet and Nutrition Survey (NDNS) 2008-9....................................................24.11.1Visual impairment questions asked................................................................................24.11.2Visual impairment prevalence estimates........................................................................24.11.3Methodological issues....................................................................................................24.11.4Study contacts and further information...........................................................................24.12 Life Opportunities Survey (LOS) 2010........................................................................24.12.1Visual impairment questions asked................................................................................24.12.2Visual impairment prevalence estimates........................................................................24.12.3Methodological issues....................................................................................................24.12.4Study contacts and further information...........................................................................24.13 Understanding Society 2010/11...................................................................................24.13.1Visual impairment questions asked................................................................................24.13.2Visual impairment prevalence estimates........................................................................24.13.3Methodological issues....................................................................................................24.13.4Study contacts and further information...........................................................................2
5 Comparisons between surveys..............................................25.1 Types of measures identified.......................................................................................25.1.1 Questions on disability and health conditions.................................................................25.1.2 Questions on visual capability........................................................................................25.1.3 Questions on specific ocular conditions..........................................................................25.1.4 Questions on self-rated eyesight and ‘difficulty seeing’..................................................25.2 Inclusion and exclusion criteria...................................................................................25.2.1 Use of low vision aids (LVAs).........................................................................................25.2.2 Whether conditions are ‘limiting’.....................................................................................2
6 Conclusions.............................................................................2
Appendix A Summary of surveys..............................................2Summary table of reviewed surveys, sample and questions........................................2
Appendix B Project team...........................................................2Project team................................................................................................................. 2Project advisors............................................................................................................2
Appendix C Suggested further work.........................................2Summary...................................................................................................................... 2C1 Extend the scope of the review...........................................................................2C2 Cognitive development work with visually impaired people.................................2C4 and C5 Developing the HSE coding of visual impairment......................................2C6 and C7 Secondary analyses of HSE and other survey datasets: trends, subgroups and social inclusion......................................................................................................2
Notes and References..............................................................................................................2
TablesTable 4:1 Prevalence of visual impairment, by age group (HSE 2007)......................................................2Table 4:2 Prevalence of visual impairment, by sex (HSE 2007)................................................................2Table 4:3 Prevalence of visual impairment, by age group (SHeS 2008)....................................................2Table 4:4 Prevalence of visual impairment, by sex (SHeS 2008)..............................................................2Table 4:5 Prevalence of self-reported difficulties in seeing the face of someone across a room, by age group
(WHS) 2Table 4:6 Prevalence of self-reported difficulties in seeing the face of someone across a room, by sex (WHS)
2Table 4:7 Prevalence of self-reported visual impairment at Llticde, by age group (WHS).........................2Table 4:8 Prevalence of self-reported visual impairment at Llticde, by sex (WHS)....................................2Table 4:9 Prevalence of self-reported cataracts/eyesight problems in past 12 months, by age group (APMS)
2Table 4:10 Prevalence of self-reported cataracts/eyesight problems in past 12 months, by sex (APMS).2Table 4:9 Prevalence of self-reported ocular conditions, by age group (ELSA)........................................2Table 4:12 Prevalence of self-reported ocular conditions, by sex (ELSA).................................................2Table 4:13 Prevalence of self-rated quality of eyesight, by age group (ELSA)..........................................2Table 4:14 Prevalence of self-rated quality of eyesight, by sex (ELSA).....................................................2Table 4:15 Prevalence of self-rated difficulty in seeing, by age group (FACS)..........................................2Table 4:16 Prevalence of self-rated difficulty in seeing, by sex (FACS).....................................................2Table 4:15 Prevalence of ‘difficulties with sight’ i.e. uses glasses or contacts by age...............................2Table 4:16 Prevalence of ‘difficulties with sight’ i.e. uses glasses or contacts by sex...............................2Table 4:15 LOS % of respondents reporting difficulties in seeing things up close and at distances by age2Table 4:16 LOS % of respondents reporting difficulties in seeing things up close and at distances by sex2Table 4:15 Prevalence of visual impairment by age using LOS definition.................................................2Table 4:16 Prevalence of visual impairment by sex using LOS definition..................................................2Table 4:15 Prevalence of respondents reporting difficulties with sight by age group in Understanding Society
2Table 4:16 Prevalence of Prevalence of respondents reporting difficulties with sight by sex in Understanding
Society 2Table 5:1 Visual impairment measures among older people, by survey and age group...........................2Table 5:2 Visual impairment measures among younger people, by survey and age groupError! Bookmark
not defined.
FiguresFigure 4:1 HSE 2007 question on long-standing illness, disability or infirmity..........................................2Figure 4:1 Long-standing illness code frame.............................................................................................2Figure 4:3 Descriptions of codes related to visual impairment...................................................................2Figure 4:4 SHeS 2008 ‘long-standing physical or mental condition or disability’ questions.......................2Figure 4:3 WHS 2007 question on eyesight quality...................................................................................2Figure 4:4 WHS 2007 questions on health conditions and disabilities.......................................................2Figure 4:5 Comparisons between ‘See’ and ‘LLticde’ by sex (WHS).........................................................2Figure 4:8 APMS 2007 Questions on general health.................................................................................2Figure 4:9 ELSA questions on ocular conditions........................................................................................2Figure 4:10 ELSA question on self-rated eyesight.....................................................................................2Figure 4:11 Self-rated quality of eyesight, by whether have a self-reported ocular condition (ELSA)......2Figure 4:12 FACS question on long-standing illness or disability..............................................................2Figure 4:13 Comparing prevalence of visual impairments reported in HSE, SHeS and FACs..................2Figure 4:12 FRS questions on long-standing illness or disability...............................................................2Figure 4:13 FRS Disability Follow-up questions on health conditions........................................................2Figure 4:13 FRS Disability Follow-up questions on visual capacity...........................................................2Figure 4:14 Living in Wales questions on long-term illness or disability....................................................2Figure 4:15 Living in Wales questions on type of disability or impairment.................................................2Figure 4:16 LIDNS questions on long-standing illness, disability or infirmity.............................................2Figure 4:16 LOS questions on sight...........................................................................................................2Figure 4:16 LOS questions on long-term impairments and disability.........................................................2Figure 4:17 Understanding Society questions............................................................................................2Figure 5:1 Phrasing of questions on disability.....................................................................................2Figure 5:1 Prevalence of visual impairment, by survey and sex................Error! Bookmark not defined.Figure 5:2 Prevalence of visual impairment, by survey and age group......................................................2
Acknowledgements
We would first like to thank the Thomas Pocklington Trust and its trustees for guidance on shaping this review and for the financial support that made it possible. In particular, we thank Dr Angela McCullagh, Katrina Harrington and Sarah Buchanan for their advice and patience.
We would also like to thank the many people who have contributed to this project in terms of identifying relevant resources for inclusion, providing detail on the methodology of specific surveys, and advising on the clinical aspects of conditions that can cause sight loss. We are particularly indebted to the staff at the UK Data Archive for help with accessing the datasets.
Furthermore, we would like to acknowledge the time and contribution of the many thousands of respondents whose generous participation continues to make social surveys possible, and the professionalism and dedication of the interviewers and the research nurses who collect the survey data in field.
Jo d’Ardenne, Matt Hall, Sally McManus
Executive summary
The Pocklington TrustThis review was funded by a research grant from the The Pocklington Trust. The Trust supports social and public health research that identifies practical ways in which the lives of people with sight loss can be improved. The report describes what national general population survey data are available that allow us to compare the situation of people with visual impairment with that of the rest pf the population. The objective is to improve the measurement of visual impairment in British national survey research.
BackgroundRegistration rates and health service use statistics represent a minority of people affected by sight loss. Population prevalence estimates vary depending on the definitions applied and the data collection methodology used. A range of different indicators of visual impairment are used on national surveys in Britain. There have been no ‘gold standard’ questions for capturing the presences of visual impairment in general population survey research.
Aims Identify what questions about the presence of visual impairment are
currently being used in national surveys of the general population. Consider what these questions capture (for example, reference to low
vision aids; use of filter questions; mode of administration; location in questionnaire; prevalence estimates of visual impairment generated; how rates compare across surveys by sex and age).
Engage with a range of clinical and social researchers and with government social research and its agencies, on evaluating current approaches to assessing visual impairment on general population surveys.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 1
Methodology A review was undertaken to identify relevant surveys using search
engines and contacts. Inclusion criteria were applied to prioritise studies for the analysis.
Datasets were obtained from the UK Data Archive or direct from researchers. For each survey, the sample profile was described and the questions and the format of their administration were documented.
SPSS was used to manage the data: the relevant variables were identified, derived variables produced, and prevalence rates generated and presented by age and sex.
The draft report was circulated to various experts and commissioners in the field for comment and a roundtable discussion held to refine the report’s content and recommendations. (underway)
Notes only:
Results
Discussion
Recommendations Harmonised disability questions group. Sample Survey topic Interviewer and research nurse training Survey method Question location – Health section? Disability section? Socio-
demographics? Question format – prompted, unprompted, observed, objective. Filter questions Use of low vision aids, impact on functioning Code frames Aggregating categories: ‘sensory impairments’ Survey reporting Archiving and documentation.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 2
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 3
1 Background and approach
1.1 Background
1.1.1 Estimates of the prevalence of visual impairmentThere are various estimates of the size of the population with visual
impairmenti: a widely cited figure is that sight loss affects the everyday
lives of up to two million people in the UK.ii Access Economics estimated
that in 2008 there were 1.8 million people in the UK with sight loss (1.6
million who were partially sighted and 0.2 million blind people).iii
Our changing demographics – including in terms of age, ethnicity and
obesity – are impacting on trends in the prevalence of visual impairment.iv
The majority of affected people are aged 75 and over,v although it has also
been estimated that 80,000 people of working age are living with sight loss
in the UK.vi The overall visual-impaired population has been projected to
rise by a quarter over the next 30 years,vii and to more than double by
2050.viii In England, about 310,000 people are registered with Councils with
Adult Social Services Responsibilities (CASSRs) as sight impaired
(partially sighted) or as severely sight impaired (blind).ix,x Registration rates
therefore represent an underestimate of the wider number of people who
may be considered to have a visual impairment.
1.1.2 Factors influencing estimates of visual impairmentPrevalence estimates vary according to what is measured (for example,
conditions or symptoms), how it is defined and captured, and who is asked.
Visual impairment is not only multi-categorical in the symptoms manifested
(for example, tunnel vision, blurred vision, reduced contrast), but also
multi-dimensional in encompassing a spectrum of severity within each
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category. Self-evaluation of symptoms and severity are problematic, as
they depend on expectations and recall as well as being sensitive to other
sources of reporting bias.
While some thresholds of severity have been agreed for particular contexts
(for example, to qualify for registration), there are no ‘gold standard’
questions for operationalising such thresholds in survey research. The
work of Tait et al. has drawn together key studies that have contained good
quality ophthalmic assessments, mostly among older people. However,
most national, general population social surveys do not have the capacity
(in financial or time resources) to include such assessments. Recently, the
Office for National Statistics (ONS) issued a suite of harmonised questions
recommended for the measurement of disability and impairment on
government social surveys. These will be considered as part of this review.
1.1.3 Use of general population surveys in estimating prevalence
To examine the prevalence of impaired vision, and its comorbidity and
correlates, surveys are uniquely well placed. They collect a wealth of rich
and publicly available data and are a cost effective resource that can be
better utilised. In particular, general population surveys enable examination
of treatment and registration rates among all people with visual
impairment, as samples also include those who are not in contact with
support and services. General population survey data are essential if the
circumstances of visually impaired people are to be compared with those
of the population as a whole. Without such data, social and economic
inequalities can not be fully documented.
Major government and research council funded studies ask a range of core
socio-demographic questions, irrespective of the focus of the
questionnaire. These often use agreed government harmonised question
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wordings to enable cross study comparisons.xi General health, and to a
lesser extent functional impairment, have been included in a number of
these. However, visual impairment has not been prioritised. We can
hypothesis why this might be:
it is regarded as of specialist (rather than generalist) interest;
it is not recognised as widespread;
it is subject to a wider neglect of issues that disproportionately affect
older people; and finally,
because of the lack of good quality usable questions suitable for lay
survey administration (see Tate et al.xii).
In the current economic climate, which has hit social research hard, these
obstacles are even harder to overcome.
It should be noted that it is not an aim of this review to estimate the
prevalence of visual impairment in the population, rather to identify what
survey questions are currently in use and to examine the impact of
question and survey method on the proportion and characteristics of the
population with visual impairment that is identified.
1.1.4 Variation in the definition of visual impairmentThe current approaches to assessing whether or not survey respondents
have a visual impairment are inconsistent and may often be inaccurate.
Approaches in both clinical contexts and population-based studies have
used varying methods and thresholds in defining and measuring sight
related problems. Definitions have typically focused on specific medical
eye conditions, the presence of particular symptoms, functional aspects of
what the person can and cannot see in different contexts, and on
subjective assessments of quality of eyesight. There is no ‘true’ or absolute
prevalence of visual impairment. Rates and associations depend on the
definitions used and in terms of what aspects of visual impairment are
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considered and what severity thresholds are considered relevant for being
‘visually impaired’.
1.2 Aims of this survey reviewThe aims of this report are to:
Review what questions capturing any aspect of visual impairment
are currently being used; with what populations; and where.
Describe what these questions measure; what allowance is made
for use of low vision aids; what prevalence estimates of visual
impairment they generate; and how the rates compare by sex and
age group.
Engage with a range of clinical and social researchers and with
government social research and its agencies on evaluating current
approaches to assessing visual impairment on general population
surveys.
We hope that through this review and subsequent discussions to:
Review the data already collected.
Raise the profile of visual impairment measurement among social
researchers and survey commissioners to inform future data
collection.
Identify cost effective secondary analyses or methodological
development work that could be done to situate the circumstances
of visually impaired people in the context of the wider population.
1.3 Process of review
Stage 1: Initial consultation
Initial exchange with experts (research, clinical and policy).
Stage 2: Review population based surveys including a measure of visual
impairment
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Identify national general population surveys.
Obtain data sets and generate prevalence estimates.
Review methodology.
Describe potential secondary analyses.
To come:
Stage 3: Discussions
Present initial review findings.
Stage 4: Finalise review report
Circulate for further iterations of input and comment.
1.4 Summary of methodological approachA search of datasets held by the UK Data Archive was undertaken. Papers
and reports accessed through Athens, Medline, and Social Care Online
were scanned for mention of relevant British-based national surveys. We
also used word-of-mouth suggestions from other researchers, in particular
to identify surveys where the visual impairment data had not (yet) been
written up in survey reports or as academic papers.
SPSS was used to generate prevalence estimates of different definitions of
visual impairment from all the relevant national surveys for which we were
able to obtain data. This used the relevant weighting variables, where
these were archived on the dataset. The rates were national (representing
England, Scotland or Wales) and produced by age and sex, to facilitate
comparison across surveys covering different age ranges.
1.5 Consultation with experts We would like to acknowledge the (on-going) input from a range of different professionals. These include:
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Charities and campaign organisations Femi Nzegwu, British Red Cross
Sarah Buchanan, Thomas Pocklington Trust
Others, such as: Vision 2020 UK, the Royal National Institute of
Blind People (RNIB), Action for Blind People (ABP), the Eyecare
Trust, Fight for Sight, others we could invite comment from? (we
would like here to acknowledge the input of anyone at the RNIB
meeting on 21st September, if they are happy with that).*
Survey directors and managers Joanna Bulman and Ian O’Sullivan, Life Opportunities Survey (LOS),
ONS
Rachel Craig, Health Survey for England (HSE) director, NatCen
Kate Taylor, English Longitudinal Survey of Aging (ELSA) director,
NatCen
Katharine Sadler, Welsh Health Survey (WHS) director, NatCen
Catherine Bromley, Scottish Health Survey (SHeS) director,
ScotCen
Beverley Bates, National Diet and Nutrition Survey (NDNS) director,
NatCen
Joanne Maher, Family Resources Survey (FRS), NatCen
Clare Tait, Family and Children Survey (FACS), NatCen
Ruth Smith and Aleks Collingwod, Better Design Survey, NatCen
Richard Boreham, Understanding Society (US), NatCen
Academics Sam Waller, Engineering Design Centre, Cambridge University
James Nazroo, Director of the Centre for Census and Survey
Research, University of Manchester
Howard Meltzer, Professor of disability and mental health, University
of Leicester
Janet Robertson, Lancaster University
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Ian Bruce, City University*
Graeme Douglas, University of Birmingham*
Geoff Cook, Reading University*
Jude Robinson, Liverpool University*
Bruce Evans, Institute of Optometry*
Jennifer Evans, Astrid Fletcher, Emily Grundy, LSHTM*
Rosemary Tate, University of Sussex*
Clinicians Royal College of Ophthalmologists*
Moorfields Eye Hospital NHS Foundation Trust*
The College of Optometrists*
Government departments and agencies Bethan Thomas, Statistical Head of Surveys and International
Statistics, NHS Information Centre for health and social care
Martin Farmer, Office for Disability Issues (ODI), Department for
Work Pensions (DWP)
Andrew Nocon, Research Manager, Equality and Human Rights
Commission (EHRC)
Department of Health (DH)*
1.6 Report structureChapter 2 gives an overview of the range of types of data collection that provide insight into the prevalence and profile of the visually impaired population in Britain.
Chapter 3 describes the methods used in doing this review and lists the surveys screened in as eligible for the analysis.
Chapter 4 reviews each eligible survey in terms of its visual impairment questions and the prevalence estimates that each question generates.
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Chapter 5 makes comparisons between the surveys.
Chapter 6 draws out overarching conclusions.
Chapter 7 lists recommendations for improving the future measurement of visual impairment in national general population surveys.
Appendices outline: the project team; further work that could be done using existing, publicly available survey datasets (in particular HSE); and summarises the reviewed surveys and questions.
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1 Types of data collectionThere is a range of types of data collection, and many include some
information on visual impairment. To provide context for this review of
national surveys of the general population, some the other types of data
collection are briefly discussed in this chapter:
National surveys of the general population
National surveys using non-random sampling
Regional surveys
Surveys of people with visual impairment
Surveys of disabled people
Surveys of other subgroups of the population
Surveys using objectives measures
Administrative data sources
Qualitative studies
In this chapter, a brief discussion of the strengths and weaknesses of using
each of these approaches for estimating the prevalence and describing the
profile of people with visual impairment is given. Strengths and
weaknesses tend to relate either to how representative the sample is or to
the validity of the information on visual impairment collected.
The main aim of this review is to consider the impact of survey questions
on the prevalence and profile of visual impairment generated. The
remainder of the report therefore focuses only on national surveys that
include a random sample of the general population (or an age-cohort of the
general population, for example, everyone born in a particular year).
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1.7 National surveys of the general populationA benefit of using national surveys of the general population is that they
are sufficiently representative and large to yield reliable estimates of
prevalence. They also provide excellent data on individuals’
circumstances, ideal for describing the characteristics of the visually
impaired population and being able to compare them with people without
visual impairment. Such data are already collected and publicly available,
and so efficient for further analysis.
Limitations of using national surveys of the general population include the
fact that although the overall sample is usually large, because a minority of
people are visually impaired the number of people surveyed with visual
impairment might be small. Participation in surveys can be subject to
biases associated with the presence of visual impairment, with visually
impaired people less likely to take part and less likely to be sampled in the
first place (given that communal residential settings are generally
excluded). The use of showcard prompts and self-completion booklets in
interviews compounds this exclusion. Furthermore, general population
surveys tend to rely on self-report rather than objective measures, raising
concerns about the validity of the information captured. Questions are also
filtered and phrased in such a way that can contribute to underreporting or
overreporting of visual impairment.
These issues will be explored further in the rest of this report.
1.8 National surveys using non-random sampling
The surveys reviewed in this report all use random probability samples.
These are not simple random samples - which in practice are almost
impossible to achieve at a national level, as some clustering is required for
fieldwork efficacy - but where everyone in the eligible population had a
known and quantifiable chance of selection. Convenience samples, often
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using quotas, are not included because while they can collect valid
information about the relationships between variables, they tend not to be
representative of the wider population. The people most likely to take part
in quota sample surveys are those who are easy to get hold of: people who
do not work (including for health or impairment reasons) or who work from
home. It is possible that there are commercially sponsored market
research surveys that have collected data on visual impairment. However,
the data from these tend not to be publicly documented or archived for
further analysis.
1.9 Regional surveys
Some of the key surveys focusing specifically on eye health have focused
on a single city; Copenhagenxiii, Melbournexiv, Beaver Damxv, Baltimore,
Leicestershire and North Londonxvi. There can be efficiency gains to
focusing resources and trained personnel in one geographic area, and
increasingly data are needed at lower levels for the monitoring and
planning of social and other resources. However, there can be
generalizability concerns in using data from one region to estimate rates
nationally, given regional variations in population characteristics and
environment.
Case study: The Copenhagen City Eye Study.xvii
This study was based on the third Copenhagen City Heart Study (CCHS
III). Participants who reported visual impairment or blindness or had
difficulty reading newspaper type and used prescribed eye medications
were contacted from 1999 through 2000 and asked to complete a
standardised interview concerning their ophthalmologic history. Verification
of objective ophthalmologic data was done with a questionnaire.
Prevalence rates of visual impairment and blindness were 0.7% and 0.2%
for the Copenhagen adult population. For people aged 20 to 64 years,
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 14
myopia-related retinal disorders, diabetic retinopathy, optic neuropathy,
and retinitis pigmentosa were the most common causes of impaired vision.
For older people (aged 65 to 84), cataract was the most common cause of
visual impairment, whereas age-related macular degeneration was the
major cause of blindness.
1.10 Surveys of people with visual impairment
The general population surveys in this review cover a very wide range of
topics, so the coverage of visual impairment tends to be limited to a few
questions. Surveys specifically of people with visual impairment will
naturally be more sight loss focused and relevant in their coverage. The
sample of people with a visual impairment may well also be larger.
However, drawbacks include how representative of all people with a visual
impairment the survey sample is, the lack of a control sample for making
comparisons, and the inability to estimate the prevalence of visual
impairment (unless the sample was obtained by screening the general
population).
Case study: Network 1000 Network 1000 is an innovative and ambitious project that has brought
together a panel of 1000 visually impaired people from across the UK.xviii Its
main aim is to survey the changing needs and circumstances of visually
impaired people. In 2004, Vision 2020 UK and the Visual Impairment
Centre for Teaching and Research (VICTAR) at the University of
Birmingham were commissioned by the Big Lottery Fund to carry out
phase one of the broader Network 1000 project. Network 1000 phase two
started in 2007 and has been funded by the Thomas Pocklington Trust,
RNIB and GDBA. Phase two aims to further analyse the data gathered in
Phase one as well as maintain the Network 1000 sample.xix
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The Network 1000 panel is drawn from the registers of blind and partially
sighted people held by 20 social services departments. The sample is
likely to be a good reflection of the registered population. Although the
response rate achieved was very low compared with a general population
survey (about 17%), great care has been taken with the sampling and
weighting strategies to take account of this. However, it will not be
representative of people with a less severe impairment or of people who
are not registered with social services. The panel have reported on a range
of different policy topics.xx
Study contact and further information
VICTAR - Visual Impairment Centre for Teaching and Research -
University of Birmingham ([email protected])
http://www.vision2020uk.org.uk/library.asp?section=000100050005
1.11 Surveys of disabled peopleThere have been a number of surveys conducted with a sample only of
disabled people.xxi While these can yield useful information about people
with a visual impairment, there are major limitations to using such a data
source:
Some of the samples were generated in such a way that a population
level prevalence of each impairment type cannot be generated. The
proportion of disabled people with a visual impairment is sometimes
presented rather than the proportion of people in general population
who have visual impairment (for example, see the GFK study below).
There may be no general population group to make comparisons with.
The screening tools used to identify people to include in the survey
sample tend not to explicitly mention visual impairment. There is
therefore a risk that potential respondents do not regard visual
impairment as an eligible ‘disability’, and its prevalence will be
undercounted.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 16
The general shift in disability research away from medical models of
disability means that diagnostic information about conditions,
symptoms and the causes or nature of impairments is sometimes not
collected.
The parallel shift towards a more social model of disability places the
emphasis on whether or not someone experiences barriers in their
environment because of an impairment. Someone with visual
impairment who is not ‘disabled’ by their environment is technically
out of the scope of a survey of disabled people under this conceptual
model.
As with other types of survey, there is a limit on the number of
impairments that can be recorded. Furthermore, on a survey of
disabled people the risk is greater that other impairments will be
recorded as the primary one. Subsequent coding may give less
emphasis to ‘secondary’ impairments or to symptoms regarded as
secondary to another primary condition.
Many of these limitations are successfully addressed in the Life
Opportunities Survey (LOS, see Section 4.12). Although LOS is about
disability, it is also a national survey with a full general population sample.
Case study: Experiences and Expectations of Disabled PeopleIn 2006, the Office for Disability Issues (ODI) commissioned a programme
of research to explore the lives of disabled people in Britain. The research
aimed to address information gaps on how disabled people’s lives have
changed and providing detail on their current experiences.xxii The survey
found one in ten (12%) disabled people reported a ‘visual impairment’,
ranging from 7% of 16 to 34 year olds, up to 20% of disabled people aged
75 or over.xxiii The survey was useful for making comparisons between
impairment groups, for example people with visual impairment (61%) were
less likely than other disabled people to feel that their residential property
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 17
was suitable for their needs. They were also more likely than people with
other impairments to report difficulties with public transport.xxiv
The survey research team describe how consultation with a reference
group of disabled people shifted the survey sampling approach towards a
more social model:
“There was consensus among interviewees that the draft screener [used to
identify eligible respondents] was too heavily based on the medical model of
disability and that the questioning around people’s conditions was very long and
clinical, and ultimately unnecessary. In response this was replaced with a shorter
and simpler version, which would enable people to self-identify which broad
group (physical or visual impairment etc.) they felt best described their
impairment. Similar comments were made about the language suggested in
some of the survey questions being too heavily based on the medical model,
which were amended to reflect the social model better.”
As a consequence of taking a social model approach, the survey questions
moved away from the collection of clinical diagnoses of conditions.
Study contact and further information
Vicki Wright, NatCen
http://odi.dwp.gov.uk/docs/res/eedp/eedp-exec-summary.pdf
1.12 Surveys of other population subgroups
There are a number of surveys that draw their samples from specific
sampling frames or select only members of particular subgroups. Surveys
of older people, such as the English Longitudinal Study of Aging (ELSA),
have tended to include more questions about visual impairment because of
the high proportion of older people who are affected. Other relevant
surveys have been of civil servants (Whitehall II), parents (Families and
Children Survey), older people living in communal settings (HSE 2000),
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 18
unemployed people (Evaluation of the New Deal for Disabled People), and
people recruited through contact with a particular service, treatment, clinic
or due to registration.xxv
These surveys share many of the same benefits and limitations as outlined
above. In particular, while they can provide rich data on a particular
subgroup, they are not well placed for creating prevalence estimates of the
visually impaired population or for comparing visually impaired people with
the wider population.
Case study: Evaluation of the New Deal for Disabled PeopleThere has been an extensive programme of evaluation of the New Deal for
Disabled People. This included asking disabled people on Incapacity
Benefit (now Employment Support Allowance) about the nature of their
impairment. One interesting finding was that while 2% of the sample
reported visual problems as their main impairment, a further 4% reported it
as a secondary impairment. For the other impairment types asked about,
generally people were more likely to report them as primary than
secondary.
Study contacts and further information Martin Wood, NatCen
http://research.dwp.gov.uk/asd/asd5/report_abstracts/rr_abstracts/
rra_260.asp
1.13 Surveys with objective measures The surveys discussed so far (except for the regional surveys described in
Section 2.3) tend to rely on self-report measures of visual difficulties or
known diagnoses. The validity of both these approaches has been
questioned. In The prevalence of visual impairment in the UK: A review of
the literature, Tate et al. describe the UK based studies (mostly regional)
that have included visual acuity measures.xxvi These include the very large
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 19
Medical Research Council (MRC) Assessment Trial, which focused on
older people.xxvii
There are some innovative developments going on in survey research,
which seek to allow more objective assessments and tests to be
administered on national surveys by lay-interviewers. Some of these have
not progressed to a main stage of data collection, either due to timing or
funding, but one large pilot study is described below.
Case study: The Capability Better Design Survey This large-scale pilot survey assessed the feasibility of doing a large
national survey to produce data on the sensory, motor and cognitive
capabilities of a representative sample of adults in the UK.xxviii The aim was
to provide data for product designers on how to design products which can
be used by as much of the population as possible. It was carried out by the
University of Cambridge and NatCen, and funded by the Engineering and
Physical Sciences Research Council (EPSRC) in response to a grant
application. The project was called “i~design 3: extending active living
through more effective inclusive design”. A nationally representative
sample of 362 adults was interviewed for this pilot study.
One of the study objectives was to develop survey methods to assess the
threshold levels of letter size and contrast for product features that can be
easily detected. To test near vision, show cards were used that consisted
of twelve rows of letters. These tested a rage of different contrast levels.
For distance vision, show cards had to be located on a respondent’s shelf
and tape measures used to assess distance. Respondents wore any low
vision aids that they usually used for most of the day or for distance vision
or close work. The pilot study tested the feasibility of developing protocols
for objective assessments that lay-interviewers could administer in
people’s own homes.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 20
Table 2.1 shows how interviewers rated the performance of the objective
tests administered on this pilot study.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 21
Table 2.1 Interviewer feedback on the performance of the tests used in the Better Design Survey pilot
Base: All interviewers
Interviewer rating of test performance
Type of test Very well Quite wellNot very
wellNot at all
wellNot
answeredN N N N N
Vision 4 12 2 0 1Hearing 16 3 0 0 0Moberg pick up 9 10 0 0 0Grip 4 13 2 0 0Using mobile phone 11 7 0 0 1MP3 player dexterity 14 5 0 0 0Arm raises 12 7 0 0 0Cognitive 12 7 0 0 0Interface style 7 10 2 0 0Finger width 12 7 0 0 0
The vision tests were not considered to be as successful as many of the
other tests piloted. Reasons given by interviewers for this included:
Problems with light quality in people’s homes
Difficulty finding a three metre unobstructed view for the display of
eye test showcards.
Study contacts and further informationAleks Collingwood and Ruth Smith, NatCen
http://www.natcen.ac.uk/study/educational-attainment-of-blind-and-
partially-sighted-pupils
1.14 Administrative data sources
National administrative data sources can provide some very powerful
insights into visual impairment, not least because they provide a census of
a particular population subgroup and so have an enormous sample. The
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 22
future potential of administrative data sources is likely to increase greatly
with improved techniques for data linkage, including linking survey data
with databases such as Hospital Episode Statistics.
Registration rates, however, are known to undercount the prevalence of
visually impairment in the population because people with less severe
impairments (but who may still be of interest) will be less likely to be
included, and some people with severe impairments may remain
unregistered. The groups excluded from registration are different in
characteristics compared with the included groups, leading to the sample
being biased. Administrative data sources also tend to be weak in terms of
the availability of contextual data about individuals and so have limited use
for profiling the visually impaired population or comparing them with the
wider population.
Examples of two types of administrative data sources are given below, plus
a case study showing the type of further analysis that can be done using
publicly available administrative data.
Registration as blind or partially sighted Every three years, The NHS Information Centre collates council
information on the numbers of people registered as Blind or Partially
Sighted.xxix The next update on this is due to publish in October 2011.
Councils are provided with guidance and a template for the data
collection.xxx
Data on NHS sight testsThe NHS Information Centre Dental and Eye Care Team collate
information on the number of NHS sight tests, by patient eligibility. One of
these eligibilities is for patients registered blind or partially sighted.xxxi
Further information, including details of data collection, is available in the
NHS Information Centre Guide to Eye Care publications document.xxxii
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 23
Case study: Educational attainment of blind and partially sighted pupilsThe RNIB commissioned NatCen to report on the educational attainment of
blind and partially sighted secondary school pupils in England, Wales,
Scotland and Northern Ireland. Pupil information held in the National Pupil
Databases for England and Wales, the Northern Ireland School Leavers
Survey and the Scottish Annual Pupil Census were used. Regression
analysis was undertaken to look at the effect of special educational needs,
and specifically visual impairment, on secondary school attainment. In all
four countries, pupils with visual impairment performed less well than
pupils without SEN - but generally better than pupils who had other SEN.
The study highlighted problems with the Government's published figures
on educational attainment of pupils with Special Educational Needs (SEN).
Government statistics are based on the pupil's primary SEN. However, this
study found that a major factor affecting the GCSE results of blind and
partially sighted pupils was whether or not they also had other SEN not
related to their vision.
Study contacts and further informationJenny Chanfreau and Andreas Cebulla, NatCen
http://www.natcen.ac.uk/study/educational-attainment-of-blind-and-
partially-sighted-pupils
1.15 Qualitative research with visually impaired peopleQualitative research can provide rich detail on the range and nature of
experiences among people with visual impairment, and there have been a
number of such studies. Findings from qualitative interviews can inform the
development of inclusive survey research methodologies. For qualitative
research a sample is selected in such a way as to represent a range of
relevant characteristics. It does not seek to quantify or to be
representative.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 24
Case study: The opinions of people with sight loss on visual impairment researchThis piece of qualitative research, funded by the Thomas Pocklington
Trust, informs the format that survey and other research that includes
people with visual impairment should take.xxxiii Participants identified four
processes that should be attended to when planning and carrying out
research:
Research aims should be practical and useful for people with sight loss
Research methods should use a broad range of approaches to asking questions
Dissemination should offer a wide range of media, and People with sight loss should be included wherever and whenever
possible.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 25
2 Methods
1.16 Identification of surveys to include in the analysisA search of datasets held by the UK Data Archive was undertaken. Papers
about visual impairment accessed through Athens, Medline, and Social
Care Online were scanned for mention of relevant British-based surveys.
We also used suggestions from researchers, in particular to identify
surveys where the visual impairment data has not (yet) been written up in
survey reports or as academic papers (as was often the case).
1.16.1 Survey inclusion criteriaThe inclusion criteria specified that to be eligible for this review, surveys
had to:
Cover a national British population (England, Scotland, Wales, or
Great Britain).
Use a general population sample (rather than be of a subgroup).
Have been conducted in the last decade (fieldwork since 2001).
In the case of repeated surveys (where data were available from
multiple waves in a survey series) priority was given to data from
2007-2009. A few surveys archived were from 2010 or 2011
(although not many due to the delay between survey fieldwork and
the archiving of final outputs). Waves of data collection closest to
2007/2008 were prioritised where available to ensure greater
comparability across the largest number of datasets. If data available
preceded 2007 the most recent dataset available was selected.
Respondents selected through random probability sampling.
The sample included adult respondents (for example, age 16 or
over).
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 26
The dataset was accessible (held on the UK Data Archive or
available directly from the survey researchers).
Survey documentation was available (archived material provided
sufficient details of the questionnaire administration, question
wording and coding instructions, where applicable).
At least one question in the archived data addressed type of health
condition, disability, impairment, or included the words ‘sight’, ‘see’,
‘vision’ or ‘visual’ in a relevant capacity.
These criteria were used as guidelines; the authors erred on being
inclusive where a survey looked valuable to the review. Reviewed surveys
include some conducted more than a decade ago or are of a population
subgroup.
1.16.2 Eligible surveys not included in the analysis
A number of surveys were identified as potentially eligible, but were not
included in the final analysis. These were the:
ONS Omnibus / Integrated Household Survey (2008)
ONS Omnibus: RNIB disability module (1998)
Labour Force Survey (LFS 2008) / Annual Population Survey (APS)
British Cohort Studies (BCS70 and 1946 National Birth Cohort)
The key reason for a survey being excluded from the review related to data
access:
1. Data from whole relevant questionnaire module not in the public data
archive.
2. Only ‘top level’ data from the relevant questionnaire module was
archived (variables on whether respondents had a health condition
were included, but variables about the type of health condition were
not included in the archived dataset).
3. Unexplained and significant ‘missing data’ on variables of interest.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 27
The reasons that each study was excluded are detailed below.
ONS Omnibus / Integrated Household Survey (IHS 2008)The ONS Omnibus (now part of the large Integrated Household Survey,
IHS) regularly runs a module on disability on behalf of the Department of
Work and Pensions. Although data are publicly available, this particular
module was excluded from the dataset in the UK Data Archive.xxxiv
ONS Omnibus: RNIB disability module (1998)The RNIB ran a module of questions on vision in the 1998 ONS Omnibus.
Although this survey is out of scope because it was conducted more than a
decade ago, attempts were made to locate it due to its particular
relevance. Although data from the ONS Omnibus are publicly available,
data from this particular module could not be located in the UK Data
Archive. In addition to the data being unavailable, the original
questionnaires were not documented.
Annual Population Survey (APS) / Labour Force Survey (LFS)
The Annual Population Survey (APS) combines data from the Labour
Force Survey (LFS) and the English, Welsh and Scottish LFS boosts. It
does contain information on health conditions that limit daily activities.
However, the relevant variable on eyesight was not included in the
archived dataset for 2008. It is one of a number of variables have been
removed from the dataset prior to public archive as part of series of steps
to prevent risk of disclosure of respondent identity.
The Birth Cohort StudiesThe British birth cohort studies have included detailed questions on types
of impairment. The surveys are longitudinal, having followed a cohort of
people over many years, and so are well placed to look at predictors and
the impact of visual impairment. Data from the cohort surveys tend not to
be archived in the UK Data Archive. Access can be arranged directly with
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 28
the survey teams for legitimate research purposes; there tends to be a
small fee associated with this to cover the costs of data management and
advice. This was not pursued, however, as the cohort samples tend to be
of a subgroup of the population (for example, people born in a particular
year) and therefore not eligible for inclusion as they are not representative
of the general population as a whole.
1.16.3 Surveys included in the analysisTwelve surveys were included in the analysis:
Health Survey for England (HSE 2007)
Scottish Health Survey (SHeS 2008)
Welsh Health Survey (WHS 2007)
Adult Psychiatric Morbidity Survey (APMS 2007)
English Longitudinal Survey of Aging (ELSA Wave 4 2007)
Family and Children’s Survey (FACS 2007)
Family Resources Survey (FRS 2008) and the FRS Disability
Follow-up (1997)
Living in Wales (2008)
Low Income Diet and Nutrition Survey (LIDNS 2005)
National Diet and Nutrition Survey (NDNS 2008)
Life Opportunities Survey (LOS 2010)
Understanding Society (US 2010/11)
Four of the surveys reviewed technically should have been excluded because they focus on a subgroup of the population (ELSA, FACS, LIDNS and the FRS Disability follow-up). They have been included because they contain different forms of questions that could be of interest and that were not included on the surveys within the inclusion criteria.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 29
1.17 Analysis
1.17.1 Statistical approachThe statistical software package SPSS was used to manage the data,
derive variables, and generate prevalence estimates using different
indicators of visual impairment (from all the eligible national surveys for
which we were able to obtain relevant data). The rates generated are at
the national level (representing England, Scotland, Wales or Britain) and
shown broken down by age and sex to facilitate comparison across
surveys covering different age ranges. Although ethnicity was also a
variable of interest, generally the sample size for this group was too small
for reliable analysis.
Publicly archived datasets tend not to contain age as a continuous
variable, but rather aggregate it into age groups (for example, 16 to 24, 25
to 34). This is a common practice done to avoid disclosure of respondent
identity resulting from multiple variables archived in combination. However,
the age bands provided varied between surveys, and so there is some
variation in the bands used here to report prevalence.
Where children (aged 15 or under) were included in the archived survey
sample, they have been excluded from these analyses. There was some
variation between surveys as to whether data were collected from
respondents aged 16 and 17. Where data were available on 16 and 17
year olds, these have been included.
1.17.2 WeightingThe data used in the analyses have been weighted using the relevant
survey specific weighting variables, where these were made available on
the archived dataset. Bases are always presented unweighted. This
corrects for selection probabilities (for example, on some surveys people in
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 30
single person households will be more likely to be selected for an interview
than people in households with more than one adult occupant) and known
patterns on non-response (for example, by comparing the profile of an
achieved sample with the profile of the known population, it usually
emerges that young men were the least likely to take part. They can then
be weighted up in the survey analysis). Robertson and Emerson, in
Estimating the number of people with co-occurring vision and hearing
impairments in the UK, argue that people with sensory impairments may
also be less likely to take part in surveys. However, with the data currently
available, it is not possible to develop weights for general population
surveys to compensate for this bias in survey participation.xxxv
1.17.3 Missing dataRespondents who refused to answer a question, or who skipped a
question they should have answered on a paper questionnaire, have been
excluded from the analysis. Likewise, ‘don’t know’ responses have also
been excluded. For this reason there may be small differences the bases
reported for individual questions within the same survey.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 31
3 SurveysThis chapter provides a summary of each survey included in the review,
covering:
1. Survey background, including the profile of the sample.
2. Relevant questions, and how these were administered.
3. Code-frames used to classify respondent answers on type of
impairment post data-collection, where these were available.
4. The prevalence of visual impairment obtained using the data
collected.
5. A discussion of any survey specific methodological issues arising,
and how these might impact on interpretation of the rates produced.
6. Survey contacts and where further information can be obtained.
Comparisons between the surveys are made in Chapter 5, and
overarching conclusions and recommendations are drawn out in Chapters
6 and 7.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 32
1.18 Health Survey for England (HSE)The Health Survey for England (HSE) is a cross-sectional survey
undertaken annually since 1994. The NHS Information Centre
commissions HSE with funding from the Department for Health. It is
representative of people (aged 16 and over) living in private households in
England. Both an initial lay-interview and a nurse follow-up visit are
conducted with everyone in selected households (up to ten adults and two
children). Core topics are run every year, with different additional topics
included each year. Only HSE 2000 has had a module of questions asking
specifically about visual impairment. In that survey year, HSE focused on
older people and also included a sample selected from communal
residential settings.
1.18.1 Visual impairment questions asked In HSE 2007 two questions were asked that provide indicators of self-
reported visual impairment. These questions were administered as part of
the face-to-face Computer Assisted Personal Interview (CAPI) in a module
of questions on ‘general health’.
Respondents were first asked whether or not they have any long-standing
illness or disability, with ‘yes/no’ response options. A ‘yes’ response was
followed with an open-ended question, in which details of up to six ‘health
conditions’ are collected. Respondent details are keyed into the laptop by
the interviewer verbatim.
The exact wording of the questions used is given in Figure 4.1. Other than
in HSE 2000, there have been no questions in the HSE questionnaire that
specifically prompted for responses relating to visual impairment.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 33
Figure 4:1 HSE 2007 questions on long-standing illness, disability or infirmity
LongIllDo you have any long-standing illness, disability or infirmity? By long-standing I mean anything that has troubled you over a period of time, or that is likely to affect you over a period of time?1 Yes2 No
IllsTxt {Ask if LongIll = Yes}What (else) is the matter with you?OPEN RESPONSE: INTERVIEWER: RECORD VERBATIM RESPONSE FULLY. PROBE FOR DETAIL. Up to six health conditions can be recorded.
1.18.2 Long-standing illness code frameAfter data collection, the responses given at the question IllsTxt were
assigned to codes by trained coders back in the office. Each response is
assigned to one of the long-standing illness codes shown in Figure 4.2.
These codes are based on the higher levels of the International Disease
Classification (ICD) system version 10.xxxvi
Figure 4:2 Long-standing illness code frameNeoplasms1. Cancer including lumps, masses, tumours and growths and benign
(nonmalignant) lumps and cystsEndocrine/nutritional/metabolic diseases2. Diabetes3. Other endocrine/metabolicMental, behavioural and personality disorders4. Mental illness/anxiety/depression5. Mental handicapNervous system (central and peripheral including brain)6. Epilepsy/fits/convulsions
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 34
7. Migraine/Headaches8. Other problems of the nervous systemEye complaints9. Cataract/poor eye sight/blindness10. Other eye complaintsEar complaints11. Poor hearing/deafness12. Tinnitus/noises in the ear13. Meniere's disease/ear complaints causing balance problems14. Other ear complaintsComplaints of heart, blood vessels and circulatory system15. Stroke/cerebral haemorrhage/cerebral thrombosis16. Heart attack/angina17. Hypertension/high blood pressure18. Other heat problems19. Piles/ haemorrhoids20. Varicose veins/phlebitis in lower extremities21. Other blood vessels/embolicComplaints of respiratory system22. Bronchitis/emphysema23. Asthma24. Hay fever25. Other respiratory complaintsComplaints of the digestive system26. Stomach ulcer/ abdominal/ hernia/rupture27. Other digestive complaints (stomach, liver, pancreas, bile ducts,
small intestine -duodenum, jejunum and ileum)28. Complaints of bowel/colon 29. Complaints of teeth/mouth/tongueComplaints of genito-urinary system30. Kidney complaints31. Urinary Tract infections32. Other bladder problems/ incontinence33. Reproductive system disordersMusculoskeletal - complaints of bones/joints/muscles34. Arthritis/rheumatism/fibrositis35. Back problems/slipped disc/spine/neck36. Other problems of bones/joints/muscles
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 35
Other long-term health conditions37. Infectious and parasitic disease38. Disorders of blood and blood forming organs and immunity disorders39. Skin complaints40. Other complaintsAdditional codes41. Unclassifiable42. Complaint no longer present43. Not answered/ Refusal
A manual and training is provided to survey data coders with details of
what should be included under each code. Descriptions of what to include
under each of the two high level ‘eye complaint’ codes are listed in Figure
4.3.
Figure 4:3 Descriptions of codes related to visual impairmentCODE 9'Cataract/poor eye sight/blindness
CODE 10Other eye complaints
- Operation for cataracts, now need glasses
- Bad eyesight, restricted vision, partially sighted
- Bad eyesight/nearly blind because of cataracts
- Blind in one eye, loss of one eye
- Blindness caused by diabetes- Blurred vision- Detached/scarred retina- Hardening of lens- Lens implants in both eyes- Short sighted, long sighted,
myopia- ‘Trouble with eyes’- ‘Eyes not good’- Tunnel vision
- Astigmatism- Buphthalmos- Colour blind- Double vision- Dry eye syndrome, trouble
with tear ducts, watery eyes- Eye infection, conjunctivitis- Eyes are light sensitive- Floater in eye- Glaucoma- Haemorrhage behind eye- Injury to eye- Iritis- Keratoconus- Night blindness- Retinitis pigmentosa- Scarred cornea, corneal
ulcers
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 36
- Squint, lazy eye- Sty on eye
1.18.3 Visual impairment prevalence estimates Overall, using the process employed in HSE 2007, 2.2% of respondents
were coded as having some form of visual impairment. Presence of visual
impairment was classified as either code 9 (cataract/poor eye
sight/blindness) or code 10 (other eye complaint) being assigned to a
response given at Illstxt post data collection. Breakdowns of this figure by
age group and sex are shown in Tables 4.1 and 4.2.
Table 4:1 Prevalence of visual impairment, by age group (HSE 2007)Age 18-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90+ Total
% 0.7 0.8 0.7 1.6 1.2 2.3 4.8 11.4 4.3 2.2Base 134 884 1153 1250 1094 1077 727 333 46* 6698*note small base size, this makes estimates unreliable.
Table 4:2 Prevalence of visual impairment, by sex (HSE 2007)Sex Male Female Total% 2.5 2.0 2.2Base 2974 3724 6698
1.18.4 Methodological issuesThere are number of measurement issues in relation to the collection of
data on visual impairment in HSE.
Firstly, respondents may not consider a visual impairment to be an ‘illness,
disability or infirmity’. This has been identified as a particular issue among
older respondents who may attribute eyesight problems to ‘aging’.xxxvii Such
people would answer ‘no’ at the screening question, and so not even be
asked the questions about ‘what is the matter with’ them. This would result
in the under-reporting of visual impairments. Similarly respondents may not
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 37
report conditions that have been ‘undiagnosed’ or where they are unaware
that a problem exists. Visual impairment may be especially vulnerable to
this type of reporting error.
Secondly, there is an issue in relation to the reporting of co-morbidities or
conditions regarded as symptomatic of another prior or primary condition.
For example, a respondent who has diabetes may state ‘diabetes’ at
Illstxt, but not specify related conditions such retinopathy (or loss of kidney
function). This would mean that the condition is coded once (as an
endocrine condition) but additional codes (eyesight problems, genitourinary
problems) are not recorded. Currently interviewers are instructed to ‘probe
for details’ in relation to each condition given. However, it is likely that
respondents could still overlook secondary impairments, especially if they
are not considered the ‘main’ element of their condition. Generally, but not
consistently, conditions are recorded rather than symptoms.
Thirdly, respondents’ original open responses to Illstxt are not provided in
the UK Data Archive (although they can be obtained by request)1.
Furthermore, the dataset combines codes nine and ten into a single item
on visual impairment. Therefore, conditions such as a blindness and
cataracts are grouped with ‘squints’ or having a ‘lazy eye’. This could lead
the definition of a ‘visual impairment’ being too broad to be useful.
In addition prevalence rates obtained in HSE could be influenced by:
Impact of sight loss on survey participation
Context (location in a health module and health survey). This could
potentially influence respondents’ expectations of what they should
report. For example respondents may report impairments with a
formal diagnosis, but not conditions that have not been diagnosed.
1 One reason for this is to protect anonymity; for example it could be theoretically possible to identify a respondent by combining details of a rare condition with other variables held on them (e.g. geographical region, age etc).
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 38
Likewise, respondents many not report visual impairments that are
corrected by low vision aids.
1.18.5 Study contacts and further informationRachel Craig, Health Survey for England (HSE) director, NatCen.
http://www.ic.nhs.uk/statistics-and-data-collections/health-and-lifestyles-
related-surveys/health-survey-for-england
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 39
1.19Scottish Health Survey (SHeS)The Scottish Health Survey (SHeS) is a continuous, cross-sectional survey
commissioned by the Scottish Government. The methods used in the
SHeS were originally modelled on the methods used for HSE, in order to
provide comparable data for Scotland. Households were selected from
across Scotland using random probability sampling. All resident adults
(age 16 or over) were invited to take part in an interview. A sub-sample of
respondents was also invited to take part in a nurse visit.
1.19.1 Visual impairment questions asked Questions in SHeS are administered in a face-to-face CAPI interview. A
similar approach to questioning is adopted as used in HSE: respondents
are first asked whether or not they have a long-term health condition or
disability. Only those who say ‘yes’ are then asked an open-ended follow
up question in which they are asked to give details of their health condition
or disability. Both these questions are asked as part of a module of
questions on general health.
Figure 4:4 SHeS 2008 ‘long-standing physical or mental condition or disability’ questions
LongIl08Do you have a long-standing physical or mental condition or disability that has troubled you for at least 12 months, or that is likely to affect you for at least 12 months?1. Yes2. No
{Ask if LongIl08=Yes} IllsMWhat [else] is the matter with you?OPEN RESPONSE: INTERVIEWER: RECORD FULLY. PROBE FOR DETAIL.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 40
Questions repeated to capture up to six conditions.
All information collected at IllsM is coded post data-collection using the
same code-frame used in HSE (see Section 4.1).
1.19.2 Visual impairment prevalence estimates
In total, in SHeS 2008, 2.3% of respondents reported having some form of
visual impairment, in line with the figure collected by HSE (see 4.1). As
with HSE, visual impairment is classified with either code 9 (Cataract/poor
eye sight/blindness) or code 10 (Other eye complaint) being assigned to
the response given at IllsM post data collection. Breakdowns of prevalence
of visual impairment by age group and sex are shown in Tables 4.3 and
4.4.
Table 4:3 Prevalence of visual impairment, by age group (SHeS 2008)Age 18-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90+ Total% 0.0 0.1 0.3 1.2 1.6 2.8 4.2 9.9 20.5Base 105 679 909 1211 1153 1095 783 332 44* 6311
*note small base size.
Table 4:4 Prevalence of visual impairment, by sex (SHeS 2008)Sex Male Female Total% 2.3 2.2 2.3Base 2770 3541 6311
1.19.3 Methodological issuesThe potential measurement issues in relation to the SHeS data on visual
impairment are similar to those discussed in relation to HSE. To
summarise:
1. Respondents may have some form of visual impairment but not
consider it to be a ‘long-standing physical or mental condition’ or a
‘disability.’
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 41
2. Respondents may not report visual impairments that are co-morbid
with or symptoms of other conditions.
3. Data on specific conditions are not available; inclusion parameters of
what constitutes a visual impairment may be too broad.
Likewise, results may be influenced by the health survey context and the potential impact of sight loss on survey participation.
1.19.4 Study contacts and further informationCatherine Bromley, Scottish Health Survey director, ScotCen
www.scotland.gov.uk/Topics/Statistics/Browse/Health/scottish-health-survey
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 42
1.20Welsh Health Survey (WHS) 2007 The Welsh Health Survey (WHS) is an annual cross-sectional survey
commissioned by the Welsh Government (WG). The population surveyed
is representative sample of the adult population (16+) living in private
households in. All adults living in randomly selected households are invited
to take part in the survey. In addition up to two children per household are
randomly selected to take part (these have been excluded from the current
analysis).
For the WHS a short interviewer administered questionnaire is given to
establish who lives in the household. After this all adults in the household
are given a paper questionnaire to complete in their own time, this
questionnaire is either picked up the interviewer on a return visit or
returned by post. All paper questionnaires were available in both English
and Welsh.
1.20.1 Visual impairment questions asked
The 2007 WHS paper self-completion questionnaire contained one
question specifically on eyesight (SEE). This question (and how it was
visually presented on paper) is shown in Figure 4.5.
Figure 4:5 WHS 2007 question on eyesight quality
In addition the WHS paper questionnaire contained two items (LLTI and
LLTICDE) designed to capture long-term illness, health problems or
disabilities. These questions adopt broadly the same approach used in
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 43
HSE and SHeS. These questions (and how they are visually presented)
are shown in Figure 4.6.
Figure 4:6 WHS 2007 questions on health conditions and disabilities
All information collected at LLTICDE was coded post data-collection using
a code-frame based on the International Disease Classification (ICD)
system. The code frame used is the same as used in HSE (see Section
4.1).
It should be noted that although respondents were prompted to provide
details of ‘one illness only’, up to four ICD-10 codes could be entered
depending on the detail of the response given.
1.20.2 Visual impairment prevalence estimates
In total 2.6% of respondents surveyed said their eyesight was not good
enough to see the face of a person across the room. In addition a further
3.0% of respondents stated they could see the face of someone across a
room but ‘with difficulty.’ A breakdown of responses to ‘See’ by age and
sex is provided in Tables 4.5 and 4.6.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 44
Table 4:5 Prevalence of self-reported difficulties in seeing the face of someone across a room, by age group (WHS)
Age 16-19 20-29 30-39 40-49 50-59 60-69 70+ Total% % % % % % % %
SEE= Yes, but with difficulty 1.8 2.0 1.6 2.2 3.3 2.9 5.8 3.0SEE= No, not at all 2.4 2.8 1.9 2.3 2.3 1.6 4.4 2.6Base 796 1574 1929 2320 2376 2284 2524 13803
Table 4:6 Prevalence of self-reported difficulties in seeing the face of someone across a room, by sex (WHS)
Sex Male Female Total% % %
SEE= Yes, but only with difficulty 2.2 3.7 3.0SEE= No, not at all 2.3 2.8 2.6Base 6361 7442 13803
The number of respondents who reported a visual impairment at LLTICDE (the question on types of long-term health condition that limit daily
activities) was much lower. A breakdown of response to LLTICDE by age
and sex is provided in Tables 4.7 and 4.8.
Table 4:7 Prevalence of self-reported visual impairment at Llticde, by age group (WHS)
Age 16-19 20-29 30-39 40-49 50-59 60-69 70+ Total% % % % % % % %
Llticde = Cataract /poor eyesight/ blindness 0.3 0.3 0.1 0.1 0.6 0.5 1.4 0.5LltIcde =Other eye problem 0.0 0.0 0.1 0.0 0.2 0.1 0.6 0.2Any eye condition 0.3 0.3 0.2 0.2 0.7 0.6 2.0 0.7Base 800 1581 1931 2305 2343 2238 2421 13619
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 45
Table 4:8 Prevalence of self-reported visual impairment at Llticde, by sex (WHS)
Sex Male Female Total% % %
Llticde = Cataract/poor eyesight/blindness 0.4 0.6 0.5LltIcde =Other eye problem 0.2 0.2 0.2Any eye condition 0.6 0.8 0.7Base 6266 7353 13619
A comparison of response patterns between the two different questions is
shown in Figure 4.7.
Figure 4:7 Comparisons between ‘See’ and ‘LLticde’ by sex (WHS)
0.0%
1.0%
2.0%
3.0%
4.0%
5.0%
6.0%
7.0%
Male Female
Can't see/ difficultiesseeing someone acrossa room reported at SEEVisual impairmentreported at Llticd
1.20.3 Methodological issuesWhile 5.6% of WHS respondents report that they find it difficult to see
someone across a room (or are unable to see someone across a room)
only 0.7% respondents report that they have a visual impairment at Llticd.
This indicates that the current WHS questions on health conditions (Llti
and Llticde) are not capturing all respondents who have some form of
visual impairment, and/or that reported difficulty in seeing someone across
a room is too inclusive a characteristic. The discrepancy between the
results could be because:
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 46
Respondents do not feel the problems with their sight ‘limit’ their
daily activities.
Respondent are only instructed to provide details of one illness at
LLticd. This could lead to respondent prioritising the reporting of
other conditions.
Respondents may have some form of visual impairment but not
consider it to be a ‘long-term illness’ ‘health condition’ or a ‘disability.’
As with HSE and SHeS, the actual conditions reported at LLticde are not
archived for general public access. However, unlike HSE and SHeS, WHS
does provide a breakdown between codes 9 and 10. The majority of
reports of visual impairment fall into code 9 rather than code 10, which
could be taken as evidence respondents are more likely to report ‘serious’
conditions. However, without a full breakdown of what actual conditions
respondents reported it is not possible to know precisely what conditions
are being captured.
In addition, other issues are raised by the questionnaire mode (self-
completion as opposed to interviewer-administered). It is possible that
sight loss influences survey participation more in self-completion modes
than in other forms of administration2. Likewise, it is possible that the self-
administered mode could increase the likelihood of proxy respondents
being used (i.e. where another household member completes the paper
questionnaire on behalf of the person who is visually impaired). These will
not always be recorded as proxy responses.
Although the question ‘SEE’ may also be open to respondent
interpretation. For example, the question asks respondents whether they
can ‘see the face of someone across a room’ but does not specify whether
a face as to be seen clearly (enough to recognise the face) or the size of 2 In WHS interviewers who conduct the initial household questionnaire can offer to read out questions to blind respondents if required. However, no record is available on the archive of how often this occurs in practice.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 47
the room. Therefore, there is scope for respondents with visual
impairments to answer ‘yes’ if they do not consider their sight problems as
serious. Likewise, respondents with certain types of impairment (e.g.
tunnel vision) may not report any sight impairments at this question.
*Issues of use of low vision aids – question only asked about
glasses/contacts where these are usually worn (i.e. excludes those who
need glasses but fail to use them).
1.20.4 Study contacts and further informationKatharine Sadler and Melanie Doyle, Welsh Health Survey directors,
Health and Wellbeing Team, NatCen.
http://wales.gov.uk/topics/statistics/theme/health/health-survey/?lang=en
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 48
1.21Adult Psychiatric Morbidity Survey (APMS) 2007The Adult Psychiatric Morbidity Survey 2007 (APMS 2007) is a survey on
the prevalence of poor mental health of people living in England,
commissioned by the NHS Information Centre for health and social care.
The survey collected information from a representative sample of adults
living in private households. Interviews were conducted face-to-face,
although sensitive questions were asked using a computerised self-
completion form.
1.21.1 Visual impairment questions asked The APMS contained two questions relevant to this study. The question
was asked in the ‘General Health’ section of the face-to-face interview. The
question is shown in the following box.
Figure 4:8 APMS 2007 Questions on general healthVisual impairments are captured using code 7 at question ‘Health’HealthNow please look at the health conditions listed on this card. Have you ever had any of them since the age of 16?SHOWCARD GCODE ALL THAT APPLY1 Cancer2 Diabetes3 Epilepsy/fits4 Migraine or frequent headaches5 Dementia or Alzheimer's disease6 Anxiety, depression or other mental health issue7 Cataracts/eyesight problems (even if corrected with glasses or contacts)8 Ear/hearing problems (even if corrected with a hearing aid)9 Stroke10 Heart attack/angina11 High blood pressure12 Bronchitis/emphysema
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 49
13 Asthma14 Allergies15 Stomach ulcer or other digestive problems16 Liver problems17 Bowel/colon problems18 Bladder problems/incontinence19 Arthritis20 Bone, back, joint or muscle problems21 Infectious disease22 Skin problems23 Other, please specify96 None of these
IF Health = RESPONSE THENHYearHave you had (name of health condition) in the last 12 months?Please say 'yes' if you have had this condition, even if you have not experienced any symptoms because you use medication or an aid.INTERVIEWER: AN AID IS SOMETHING WHICH ASSISTS SOMEONE TO OVERCOME AN IMPAIRMENT, SUCH AS A WALKING STICK ZIMMER FRAME, GLASSES OR HEARING AID.1 Yes2 No
It should be noted that although ‘Health’ was administered using a
showcard, interviewers were able to read out the list if respondents
exhibited difficulties with vision or literacy.
1.21.2 Visual impairment prevalence estimates In total 17.6% of respondents reported having ‘cataracts or eyesight
problems’ in the last 12 months. Respondents were instructed to include
eyesight problems that were corrected with glasses or contact lenses.
A breakdown of responses by age and sex are shown in Tables 4.9 and
4.10.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 50
Table 4:9 Prevalence of self-reported cataracts/eyesight problems in past 12 months, by age group (APMS)
Age 18-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90+ TotalCataracts/ eyesight problems
% 9.0 11.2 9.5 14.5 18.7 18.4 27.0 34.1 45.8 17.6Base 111 810 1262 1291 1160 1189 940 461 48* 7272*note small base size.
Table 4:10 Prevalence of self-reported cataracts/eyesight problems in past 12 months, by sex (APMS)
Sex Male Female TotalCataracts/ eyesight problems
% 16.4 18.4 17.6Base 111 810 7272
1.21.3 Methodological issuesThe total number of respondents reporting visual impairments is higher for
APMS than for the other surveys reviewed (17.6% respondents reporting
having ‘Cataracts/eyesight problems’). This is likely to be mainly due to:
1. Respondents were prompted to include problems corrected by
glasses or contacts, which may not have been mentioned otherwise.
2. Respondents are provided with a list of different types of ‘health
conditions’ at ‘Health’ rather than being asked an open question on
whether they have any health conditions. This approach could
prompt people to include problems with vision they might otherwise
not have included.
The APMS measure is limited in that it provides no indication of the type of
visual impairment respondents may have. Likewise, as with other surveys
described, there is no indication of the severity of the visual impairment.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 51
The definition of visual impairment used in this survey (particularly the
inclusion of eyesight problems that are fully correctable using glasses or
contact lenses) may be too broad to be of use for many researchers or
policy experts with an interest in visual impairment issues.
In addition, as with other surveys, results may be influenced by the impact
of visual impairment on survey participation.
1.21.4 Study contact and further informationSally McManus, Health and Wellbeing team, NatCen.
http://www.mentalhealthsurveys.co.uk/
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 52
1.22English Longitudinal Study of Aging (ELSA) Wave 4Data from the English Longitudinal Study of Ageing (ELSA) have been
used quite extensively to look at the prevalence and circumstances of older
people with visual impairment. It has demonstrated how poor eyesight can
influence health, quality of life, mobility and the ability to look after oneself
and take part in social activities, as well as economic wellbeing.xxxviii
Interestingly, data from the survey has also suggested that older people
with poor eyesight may tend to have good social networks and access to
informal care. The ELSA findings demonstrate the need for better
diagnosis and treatment of sight problems and better strategies to screen
older people for visual impairment.
ELSA is a longitudinal study of people aged 50 and over and their younger
partners, living in private households in England. Respondents are
interviewed every 2 years to measure change in their health, economic and
social circumstances. The survey programme is the result of collaboration
between University College London, the Institute for Fiscal Studies (IFS),
and the National Centre for Social Research (NatCen). Funding for the first
four waves of ELSA has been provided by the US National Institute on
Aging, and a consortium of British Government departments.
Technically, the survey is not eligible for inclusion because it samples a
subgroup of the population (respondents aged 50 or more, and their
partners). However, it has been included as it uses a different style of
questions to those discussed previously. Cohort studies are also of
particular value because their longitudinal structure allows for investigation
of causality and change over time.
The ELSA data analysed for this review was collected during wave four of
the study, conducted between 2008 and 2009. The survey comprised a
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 53
face-to-face interview, a self-completion questionnaire, and a nurse visit.
The questions of interest were included in the face-to-face interview.
1.22.1 Visual impairment questions asked ELSA also includes questions on whether respondents have ever been
diagnosed with specific ocular conditions: glaucoma, diabetic eye disease,
macular degeneration and cataracts.
The questions are shown in the box on the next page. Please note that
ELSA Wave four uses dependent interviewing in many of its modules. This
means that certain questions were checking the information respondents
had given at earlier waves rather than asking questions for the first time.
The questions from the ELSA wave one are also shown in Figure 4.9 with
examples of the checks used at Wave 4.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 54
Figure 4:9 ELSA questions on ocular conditionsOCCULAR CONDITIONSHeop (Wave 1)Has a doctor or optician ever told you that you have (or have had)...READ OUT EACH IN TURN AND CODE ALL THAT APPLY...INCLUDE DIABETIC RETINOPATHY IN CODE 2INCLUDE AGE RELATED MACULOPATHY IN CODE 31 Glaucoma or suspected glaucoma?2 diabetic eye disease?3 macular degeneration?4 cataracts?96 None of these
HEOPC (Wave 4)Our records show that when we last interviewed you, you said that hadhad (or had been told by a doctor had had) {CONDITION} .INTERVIEWER: Code 1 below unless respondent spontaneously disputes this record.1 Yes2 No
HEOPS (Wave 4)IF confirms previous eye condition = Yes [HeOpC =1]Do you still have {CONDITION} ?1 Yes2 No
HEOPT (Wave 4)Has a doctor or optician told you that you have (or had)...INTERVIEWER: Read out each (except those previously coded) and code all that apply.INCLUDE DIABETIC RETINOPATHY IN CODE 2INCLUDE AGE RELATED MACULOPATHY IN CODE 31 Glaucoma or suspected glaucoma?2 diabetic eye disease?3 macular degeneration?4 cataracts?
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 55
96 None of these
In addition ELSA includes a question in which respondents are asked to
rate their own eyesight (see Figure 4.10).
Figure 4:10 ELSA question on self-rated eyesightHEEYEIs your eyesight (using glasses or corrective lenses if use them)...INTERVIEWER: Read out...1 ...excellent,2 very good,3 good,4 fair,5 or, poor?6 SPONTANEOUS CODE: Registered or legally blind
1.22.2 Visual impairment prevalence estimates In total, 20.5% of ELSA respondents reported having an ocular condition at
wave 4. The proportion of ELSA respondents reporting specific ocular
conditions, are summarised in Tables 4.11 and 4.12.
Table 4:11 Prevalence of self-reported ocular conditions, by age group (ELSA)
Age 50 to 59 60 to 69 70 to 79 80 to 89 90 plus TotalOcular conditions % % % % % %Glaucoma/ suspected glaucoma 2.0 3.9 6.6 8.8 13.2 4.6Diabetic Eye Disease 1.0 1.4 2.5 1.5 1.5 1.6Macular Degeneration 0.9 1.6 4.6 10.0 11.8 3.1Cataracts 3.2 10.6 25.9 31.2 36.0 14.5Any of the above 6.6 15.7 34.3 41.6 52.2 20.5Base 2899 3506 2358 982 136 9881
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 56
Table 4:12 Prevalence of self-reported ocular conditions, by sex (ELSA)
Sex Male Female TotalOcular conditions % % %Glaucoma/ suspected glaucoma 4.7 4.5 4.6Diabetic Eye Disease 1.7 1.4 1.6Macular Degeneration 2.5 3.6 3.1Cataracts 11.9 16.6 14.5Any of the above 17.6 22.8 20.5Base 4421 5460 9881
In addition to being asked about specific ocular conditions, respondents
were also asked to rate the overall quality of their eyesight (when using
corrective lenses if appropriate). These are summarised in Tables 4.13 and
4.14.
Table 4:13 Prevalence of self-rated quality of eyesight, by age group (ELSA)
Age 50 to 59 60 to 69 70 to 79 80 to 89 90 plus TotalSelf-rated eyesight % % % % % %Excellent 19.2 16.1 11.4 8.9 7.4 15.0Very good 34.5 35.7 32.0 26.3 18.4 33.3Good 36.7 37.8 40.2 39.7 26.5 38.1Fair 8.1 8.5 11.8 15.5 23.5 10.1Poor 1.4 1.7 4.0 8.1 19.9 3.1SPONTANEOUSRegistered blind 0.1 0.3 0.6 1.5 4.4 0.5Base 2900 3509 2359 986 136 9,890
Table 4:14 Prevalence of self-rated quality of eyesight, by sex (ELSA)Sex Male Female Total
Self-rated eyesight % % %Excellent 16.7 13.7 15.0Very good 34.0 32.7 33.3Good 36.9 39.1 38.1
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 57
Fair 9.6 10.4 10.1Poor 2.4 3.6 3.1SPONTANEOUSRegistered blind or partially sighted 0.5 0.5 0.5Base 4426 5464 9890
In total 0.5% of ELSA respondents reported being registered as blind or
partially sighted when asked to rate their own eyesight. This was not a
direct question, and therefore is likely to represent an underestimate of the
true rate.
The proportion of respondents describing their eyesight as ‘fair’ (10.1%) or
‘poor’ (3.1%) was lower than the proportion stating that they had an ‘ocular
condition’ (20.5%). This led to us to examine the differences in perceptions
of eyesight quality between respondents who did and did not report having
ocular conditions. The relationship between self-rated eyesight quality and
ocular condition is illustrated in Figure 4.11.
Figure 4:11 Self-rated quality of eyesight, by whether have a self-reported ocular condition (ELSA)
Figure 4.11 shows that the majority of people who reported having an
ocular condition still rated their eyesight highly. 39.3% of people with an
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 58
ocular condition rated their eyesight as ‘good’, 21.9% rated their eyesight
as ‘very good’, and 7.8% even rated their eyesight as ‘excellent’.
In addition, there is little variation between the proportion of respondents
who rate their eyesight as being ‘good’ between the two groups (39.3% of
people with ocular conditions rated their eyesight as ‘good’; 37.8% of
people without ocular conditions rated their eyesight as ‘good.’). This
indicates that the self-rating of eyesight is distinct from the reporting of the
presence of ocular conditions. This is discussed further in Chapter 6.
1.22.3 Methodological issues
ELSA asks different types of questions to those included in the general
population survey previously discussed i.e. it asks respondents whether
they have specific ocular conditions (glaucoma, Diabetic eye disease or
cataracts). In ELSA 20.5% of respondents reported having a specific
ocular condition. As the target population is different to the surveys
previously discussed (only respondents aged 50 and over and their
partners are interviewed) a higher prevalence rate of visual impairments is
to be expected. However, when making comparisons between
respondents aged 50+ in HSE and SHeS reports of eyesight conditions are
still higher in ELSA (see Chapter 5 for a direct comparison).
Currently ELSA only asks about four types of ocular condition. Therefore,
other types of visual impairment may be excluded. Nonetheless, this type
of question leads to a higher level of reporting than found using general
health condition approach used in the general population surveys
reviewed.
1.22.4 Study contacts and further informationKate Taylor, English Longitudinal Survey of Aging (ELSA) director, NatCen
James Nazroo, Manchester University.
http://www.ifs.org.uk/elsa/
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 59
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 60
1.23 Family and Children Survey (FACs) 2006-2007
The Families and Children Study (FACS), formerly known as the Survey of
Low Income Families (SOLIF), originally provided a new baseline survey of
Britain's lone-parent families and low-income couples with dependent
children. The survey was named SOLIF for Waves 1 and 2, and FACS
from Wave 3 onwards.
The FACS study has become a 'true panel', whereby respondents in 1999
have been re-interviewed in subsequent annual waves. Starting with Wave
3 (2001) the survey was extended to include higher-income families,
thereby yielding a complete sample of all British families (and the
subsequent name change). From Wave 4 (2002) onwards, longitudinal
comparisons can be made.
Technically, the survey is not eligible for inclusion because it samples a
subgroup of the population (families with children), rather than the general
population. However, it has been included as it uses a different style of
questions to those discussed previously.
All the questions reviewed here were administered in a face-to-face CAPI
interview.
1.23.1 Visual impairment questions asked
FACs contains two questions on visual impairment, are included in a
general health question module. The questions mirror the approach used
in HSE and SHeS: respondents are first asked whether they have any form
of longstanding illness, disability or infirmity and then, if they respond in the
affirmative, are asked a follow-up question about the types of conditions
that they have. However, unlike HSE and SHeS, at the follow up question
respondents are provided with a closed list of categories on illness or
disability rather than being asked an open question.
The wordings of these questions are shown in Figure 4:12 below.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 61
Figure 4:12 FACS question on long-standing illness or disabilityHea2Do you have any longstanding illness, disability, or infirmity of any kind? By longstanding I mean anything that has troubled you over a period of time or that is likely to affect you over a period of time?1 Yes2 No
Hea3SHOWCARD What kind of illness or disability do you have?1 Problem with arms, legs, hands, feet, back or neck (including arthritis or rheumatism)2 Difficulty in seeing3 Difficulty in hearing4 Skin conditions, allergies5 Chest, breathing problem, asthma, bronchitis6 Heart, blood pressure or blood circulation problems7 Stomach, liver, kidney or digestive problems8 Diabetes9 Depression, bad nerves10 Mental illness or suffer from phobia, panics or other nervous disorders11 Learning difficulties (or mental handicap)12 Epilepsy13 Other health problems or disabilities
1.23.2 Visual impairment prevalence estimates In total, 0.6% of respondents who took part in FACS reported having difficulty in seeing at Hea3. A breakdown of prevalence by age and sex is shown in Tables 4.15 and 4.16.
Table 4:15 Prevalence of self-rated difficulty in seeing, by age group (FACS)
AgeUnder
18 18-19 20-29 30-39 40-49 50-59 60-69 70-79 TOTAL% % % % % % % %
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 62
Difficulty seeing at Hea3 0.0 0.0 0.2 0.5 0.6 1.5 7.9 0.0Base 10* 64* 1285 2957 2659 602 38* 4* 7619*Note the small base size for these estimates, which makes them unreliable.
Table 4:16 Prevalence of self-rated difficulty in seeing, by sex (FACS)Sex Male Female Total
% % %Difficulty seeing at Hea3 2.2 0.6 0.6Base 137 7482 7619
There was a difference between men and women in the reporting of
‘difficulty seeing’ (2.2% of men, 0.6% of women). This is likely to be due to
sampling issues: adult respondents on FACS were the available parent
with primary responsibility for childcare. This was usually the mother.
When fathers were available to be the survey respondent, it is probable
that poor health or the presence of an impairment may have made it more
likely that they were home (and not in work). This is likely to account for the
disparity in rates of reporting difficulty in seeing.
1.23.3 Methodological issuesAs with HSE and SHeS, respondents who have visual impairments will
only report them if they consider them to be a ‘long-standing illness,
disability or infirmity.’ It is not clear if respondents will do this, depending on
the nature of their sight loss, how it impacts on them and their opinion of its
severity. This could lead to survey data under-estimating prevalence of
visual impairments.
Unlike HSE and SHeS no information is captured about the type of visual
impairment respondents may have. Likewise, no indication of the severity
of the visual impairment is captured.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 63
The FACs question is different to that used on the other surveys reviewed
in its use of a prompted list of categories after the initial question on
illnesses and disabilities. Understanding Society also adopts this approach,
however the showcard category on visual impairment is phrased in a
different way (in Understanding Society respondents are instructed to
exclude problems corrected by glasses).
It is likely that respondents who report having some form of illness or
disability may be more likely to report a visual impairment if they are
prompted to do so via use of the showcard. To test this hypotheses,
comparisons between FACs responses and HSE and SHeS responses
were examined. As discussed, the population surveyed in FACS is
different to the other surveys reviewed. FACS is a survey of parents in
receipt of Child Benefits, so is younger and more female than the
population in HSE and SHeS. Figure 4.13 therefore focuses on
respondents aged 20-59.
Figure 4:13 Comparing prevalence of visual impairments reported in HSE, SHeS and FACs
0.0%0.2%0.4%0.6%0.8%1.0%1.2%1.4%1.6%1.8%
20-29 30-39 40-49 50-59
Age Group
Prev
alen
ce o
f rep
orte
d vi
sual
im
pairm
ents
HSESHeS
FACs
Figure 4.13 does not support the hypothesis that the prompted list (with an
initial filter question) used in FACs would lead to increased reporting of
visual impairments. Reasons for this could include:
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 64
Placement of prompted list. Respondents were still only exposed
to the prompted list if they reported a health condition or impairment
first. Therefore, this approach would not increase reporting of visual
impairment among people for whom that is their only impairment.
Phrasing of prompted list. The prompted list cites ‘difficulty
seeing.’ It is possible some respondents with ocular conditions may
not feel they find it difficult to ‘see’.
Interviewer probing. In HSE and SHeS interviewers are trained to
‘probe’ respondents by asking ‘and what else?’ This is designed to
encourage fuller reporting in response to an open question, but may
not have happened in the FACS question, which is administered by
showcard.
Population surveyed. There could be confounding effects due to
the different samples even when age is taken into account. For
example, if people with visual impairments are any less likely to
become parents then they would be less likely to take part in FACs.
As with all the surveys discussed, results may also be influenced by the
impact of visual impairment on general survey participation.
1.23.4 Study contact and further informationClare Tait, Family and Children Survey director, NatCen
http://www.esds.ac.uk/longitudinal/access/facs/l4427.asphttp://www.natcen.ac.uk/facs/
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 65
1.24 Family Resources Survey
The Family Resources Survey (FRS) is a continuous, cross-sectional survey that collects information on the incomes and circumstances of private households in the United Kingdom. DWP sponsors the survey. All adults in the randomly selected households are invited to take part in a face-to-face CAPI interview. A health module is included in the FRS questionnaire to that aims to identify disabled respondents.
1.24.1 Disability questions asked FRS contains two questions that collect information on disabilities and impairments. The wordings of these questions are shown in Figure 4.14. These questions are taken from FRS 2008/2009.
Figure 4:14 FRS questions on long-standing illness or disabilityHealth NOW THERE ARE SOME QUESTIONS ABOUT HEALTH. Do you have any long-standing illness, disability or infirmity? By 'long-standing' I mean anything that has troubled you over a period of at least 12 months or that is likely to affect you over a period of at least 12 months. YesNo
{If Health=Yes}DisDif Does this/Do these health problem(s) or disability(ies) mean that you have substantial difficulties with any of these areas of your life? Please read out the numbers from the card next to the ones which apply to you. 1: Mobility (moving about) 2: Lifting, carrying or moving objects 3: Manual dexterity (using your hands to carry out everyday tasks) 4: Continence (bladder and bowel control) 5: Communication (speech, hearing or eyesight) 6: Memory or ability to concentrate, learn or understand 7: Recognising when you are in physical danger 8: Your physical co-ordination (e.g. balance) 9: Other health problem or disability
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 66
10: None of these
As with the other surveys discussed the FRS approach is to first ask
whether respondents have any form of long-standing illness or disability.
Respondents are then asked to describe the type of disability from a
prompted list. However, the list classifies disabilities in terms of the
limitations the place on the respondents’ social functioning rather than type
of medical condition per se. Therefore standard FRS data cannot be used
as a source of data on visual impairment.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 67
1.25FRS Disability Follow-up (1997)Although the standard FRS cannot currently be used to measure
prevalence of visual impairments, one off-shoot of the survey was found to
be potential interest to the review. This was the FRS Disability Follow-Up
(1997). The aim of the survey was to find out the size and characteristics of
the disabled adult population of GB. The main topics covered are:
prevalence, severity and types of disability; socio-demographic
characteristics; economic activity; financial circumstances; use of social
and health services; needs for assistance; and social participation.
Respondents who took part in the 1996/97 FRS who matched any one of a
series of sift criteria (based on age, benefit receipt or reported health
problems) were asked to take part in a further face-to-face CAPI interview.
This interview required respondent to detail the cause, type and severity of
their disability, the extra needs and costs which resulted from it, and their
participation in leisure and social activities. Over 7000 people were
interviewed.
Despite the fact this survey did not meet the inclusion characteristics it has
been included in the review. This is because it contains a number of survey
questions on visual capacity that were not identified elsewhere. However,
as the sample frame is different (i.e. the survey only collects information
from those in receipts of benefits related to disability or those aged 75+)
the prevalence estimates discussed are not comparable with the other
general population surveys reviewed.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 68
1.25.1 Visual impairment questions asked in Disability Follow-UpThe FRS Disability study included three measures aiming to capture
disabilities or health conditions. Please note the term ‘disability was not
used’. Instead the question asked about ‘health problems or complaints.’
Figure 4:15 FRS Disability Follow-up questions on health conditionsIntComp1Do you have any long term health problems or complaints which affectyour everyday activities?Yes No
Complntl (IF IntComp1=Yes)What is your health problem or complaint?ASK OR RECORD. TRY TO OBTAIN A MEDICAL NAME. TYPE IN NAME OF FIRST COMPLAINT/DISEASE/PROBLEMUp to 4 complaints coded
IntComp2Do you have any other long term health problem or complaints?ASK OR RECORD AS NECESSARYYesNo
Answers to CompIntl were coded using the ICD codeframe (as discussed
in relation to HSE). However, details of specific conditions are not provided
on the UK Data archive. In addition to this, the FRS disability follow-up
question contained nine questions on visual capacity.
Figure 4:16 FRS Disability Follow-up questions on visual capacitySeeFrnd(Wearing glasses or lenses... )Do you have difficulty recognising a friend across the road?Yes No
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 69
Reading(Wearing glasses or lenses… )Do you have difficulty reading ordinary newspaper print?Yes No
Windows (APPLIES IF SeeFrnd=Yes or Reading=Yes)Can I check, (wearing glasses or lenses... ) in a room during daytime,can you tell by the light where the windows are?Yes No
Shape (APPLIES IF Windows=Yes)(Wearing glasses or lenses... )Can you see the shapes of the furniture in this room?Yes No
RecFace (APPLIES IF Shape=l)(Wearing glasses or lenses… )Can you see well enough to recognise a friend if you get close to his orher face?Yes No
ArmLeng (APPLIES IF RecFace~l)(Wearing glasses or lenses... )Can you see well enough to recognise a friend who is an arms lengthaway?Yes No
Headline (Wearing glasses or lenses... )Can you see well enough to read a newspaper headline?Yes No
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 70
LargePrt (APPLIES IF Headline=l)(Wearing glasses or lenses... )Can you see well enough to read a large print book?Yes No
Room (APPLIES IF LargePrt=l)(Wearing glasses or lenses... )Can you see well enough to recognise a friend across the room?Yes No
1.25.2 Visual impairment prevalence estimates
1.25.3 Methodological issues FRS 2008/2009 health questions problematic for those with a
specific interest in visual impairment, as social functioning classification system used does not specifically capture sight problems. Instead, problems with vision are broadly classified under problems with communication (along wit problems hearing and problems speaking).
The FRS disability follow-up questions were more useful. However, as the population general population prevalence can
Question on health conditions do not specifically mention ‘disability’. However, cannot establish whether this could encourage reporting of visual impairments the sample used in not equivalent to the other samples where disability is specifically mentioned.
The questions measuring visual capacity are more detailed than those used in than those found in other surveys, with more scenarios given (e.g. WHS, LOS).
1.25.4 Study contact and further informationJoanne Maher, Family Resources Survey, NatCen
http://www.statistics.gov.uk/ssd/surveys/survey_family_resources.asp
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 71
http://www.esds.ac.uk/findingData/snDescription.asp?sn=4090
i Grundy E, Ahlburg D, Ali M, Breeze E, Sloggett A. Disability in Great
Britain: results from the 1996/7 disability survey. 1999: Dept of Social
Security: London.ii Keil S. (2008)
www.rnib.org.uk/xpedio/groups/public/documents/PublicWebsite/public_res
earchstats.hcsp RNIB.iii Winyard S, McLaughlan B. (2009) The economic impact of visual
impairment in the UK adult population. RNIB and Access Economics.iv RNIB (2010) Cost oversight? The cost of eye disease and sight loss in the UK today and in the future. RNIB Campaign report 29.v Evans J. International Centre for Eye Health, LSHTM (2006) Prevalence,
causes and impact of sight loss in older people in Britain, Pocklington
Occasional Paper 8.vi Keil S. (2008)
www.rnib.org.uk/xpedio/groups/public/documents/PublicWebsite/public_res
earchstats.hcsp, RNIB.vii Association of Directors of Social Services (ADSS) website:
http://www.adass.org.uk/eyes/Progress.txt.viii Winyard S, McLaughlan B. (2009) The economic impact of visual impairment in the UK adult population. RNIB and Access Economics.ix Registered Blind and Partially Sighted People, year ending 31 March
2008: the Information Centre for health and social care. x In the year ending March 2008, there have been 153,000 blind
registrations and 156,300 partially sighted registrations since 2006.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 72
1.26 Living in Wales Survey 2008
The Living in Wales Survey was commissioned by the Welsh Government.
It is the main source of information on households and the condition of
homes in Wales. This annual survey was carried out from 2004 to 2008.
The Living in Wales Survey has now been replaced by the National Survey
for Wales, the main stage of which will begin in 2012.
xi See http://www.ons.gov.uk/about-statistics/harmonisation/index.html for
details of the question wording harmonisation programme.xii Tate R, Smeeth L, Evans J, Fletcher A, Owen C, Rudnicka A. (2006) The
prevalence of visual impairment in the UK. A review of the literature. RNIB.xiii Buch H, Vinding T, la Cour M, Appleyard M, Jensen G, Nielsen NV.
Prevalence and causes of visual impairment and blindness among 9980
Scandinavian adults: The Copenhagen City Eye Study. Ophthalmology.
111:1; 53-61.xiv Livingston PM, Carson CA, Stanislavsky YL, Lee SE, Guest CS, Taylor
HR. (1994) Methods for a population-based study of eye disease: the
Melbourne Impairment Project. Ophthalmic Epidemiology. 1(3), 139-148.xv And the more recent Beaver Dam Offspring Study, see: Klein R,
Cruickshanks KJ, Nash SD, Krantz EM, Javier Nieto F, Huang GH,
Pankow JS, Klein BE. (2010) The prevalence of age-related macular
degeneration and associated risk factors. Arch Ophthalmol. 128(6): 750-8.xvi Reidy A, Minassian DC, Vafidis G, Joseph J, Farrow S, Wu J, Desai P,
Connolly A. (1998) Prevalence of serious eye disease and visual
impairment in a north London population: a population based, cross
sectional study BMJ 1316: 1643.xvii Buch H, Vinding T, la Cour M, Appleyard M, Jensen G, Nielsen NV.
(2004) Prevalence and causes of visual impairment and blindness among
9980 Scandinavian adults: The Copenhagen City Eye Study.
Ophthalmology. 111:1; 53-61.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 73
It was based on face-to-face interviews with the household reference
person or another appropriate adult in a sample of households across
Wales. In 2004 and 2008 a property survey was also carried out, which
meant that some respondents received a follow-up visit by a qualified
surveyor to undertake a property assessment of their home.
1.26.1 Visual impairment questions asked
xviii Bruce I, Baker, M. (2001) Access to Written Information - a Survey of
1000 People with Sight Problems, London: RNIB.
Bruce I, Baker, M. (2003) Employment and unemployment among people
with sight problems in the UK, London: RNIB.
Bruce I, Baker, M. (2005) Transport and mobility for people with sight
problems - the views of 1000 people, London: RNIB.xix Douglas G, Pavey S, Clements B and Corcoran C (2009) Visually impaired people’s access to employment. VISION 2020 UK and University of Birmingham.xx Bruce I, Harrow, J., Obolenskaya, P. (2007) 'Blind and partially sighted
people's perceptions of their inclusion by family and friends', British Journal
of Visual Impairment. 25(1) 68-85.xxi Bajekal M, Harries T, Breman R, Woodfield K. (2004) Review of
Disability Estimates and Definitions. HMSO.xxii GfK NOP Social Research. (2007) Experiences and expectations of
disabled people: a research report for the Office of Disability Issues. ODI:
London.xxiii GfK NOP Social Research. (2007) p39.xxiv GfK NOP Social Research. (2007) p167.xxv DH. (2003) Personal Social Services Physically Disabled and Sensory
Impaired User Experience Survey: What needs doing for 2003-2004. DH.xxvi Tate R, Smeeth L, Evans J, Fletcher A. (2005) The prevalence of visual impairment in the UK: A review of the literature. www.rnib.org.uk/xpedio/groups/public/documents/PublicWebsite/public_prevalencereport.doc
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 74
Figure 4:17 Living in Wales questions on long-term illness or disability
xxvii Evans J, Fletcher AE, Wormald R, Siu-Woon Ng E, Stirling S, Smeeth L, Nunes M, Breeze E, Bulpitt CJ, Jones D, Tulloch A. (2002) Prevalence of visual impairment in people aged 75 years and above in Britain: results from the MRC Trial of assessment and management of older people in the community. Br J Ophthalmology, 86:795-800.xxviii Collingwood A, Brown V and Smith R. (2010) Towards Better Design:
An Evaluation of the Pilot Study. NatCen: London.xxix http://www.ic.nhs.uk/statistics-and-data-collections/social-care/adult-
social-care-information/people-registered-as-blind-and-partially-sighted-
2008-england xxxhttp://www.ic.nhs.uk/services/social-care/social-carecollections/
collections-2011xxxihttp://www.ic.nhs.uk/statistics-and-data-collections/primary-care/eye-
care/general-ophthalmic-services-activity-statistics-for-england-and-wales-
year-ending-31-march-2010xxxii http://www.ic.nhs.uk/statistics-and-data-collections/primary-care/eye-
care xxxiii PS Ducket et al. (2010) The opinions of people with sight loss on visual
impairment research: study three. Thomas Pocklington Paper: London.xxxiv Smith N and Keyte R. (2008) The Disability Discrimination Act: Analysis
of data from the ONS Omnibus Survey 1996-2006. ODI.xxxv Robertson J and Emerson E. (2010). Estimating the number of people with co-occurring vision and hearing impairments in the UK. Centre for Disability Research.xxxvi WHO (2007) International Statistical Classification of Diseases and
Related Health Problems.10th Revision. Version for 2007
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 75
A showcard was used as a prompt for the following question. It was used with the response options reversed for half of the sample to avoid order affects (where respondents are more likely to select items from the top of a list than from lower down).
Figure 4:18 Living in Wales questions on type of disability or impairment
http://apps.who.int/classifications/apps/icd/icd10online/ xxxvii Robertson J and Emerson E. (2010). Estimating the number of people
with co-occurring vision and hearing impairments in the UK. Centre for
Disability Research. p18.xxxviii Nazroo J, Zimdars A. (2010) Social inclusion, social circumstances and
the quality of life of visually impaired older people. Pocklington Trust
research report.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 76
1.26.2 Visual impairment prevalence estimates Overall, 1.7% of people reported that they had a long-term illness or
disability which was impairment related. This equates to 8.3% of people
with an illness or disability. 8.8% of respondents reported being registered
as disabled or vision impaired.
1.26.3 Methodological issues It is interesting that a question was included that made reference to
being registered vision impaired with the council or social services.
However, it was unfortunate that the coding of this was not
disaggregated from that of being ‘a disabled person’ as this. [check
on plans to do this in the National Survey for Wales.]
Show card – is a visual prompt.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 77
1.26.4 Study contact and further information
wales.gov.uk/about/aboutresearch/social/ocsropage/living-wales/?lang=en
wales.gov.uk/about/aboutresearch/social/ocsropage/
nationalsurveyforwales
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 78
1.27 Low Income Diet and Nutrition Survey 2005The Low Income Diet and Nutrition Survey (LIDNS) was commissioned to
provide robust, nationally representative, baseline data on food
consumption, nutrient intake and nutritional status and factors affecting
these in low-income/materially-deprived consumers. It uses, therefore, not
a sample of the whole population, but only of people living in low-income
households.
Data were collected between 2003 and 2005 and the survey report was
published in July 2007. The survey included over 3,700 adults and children
throughout the UK and had a number of components. It collected detailed
quantitative information on food consumption, physical measurements (e.g.
height, weight, blood pressure), and a blood sample. Finally, information
on socio-economic, demographic and lifestyle characteristics was collected
in a detailed interview and assessments of physical activity and oral health
were made by questionnaire.
Details of medications currently taken and reasons for taking medication
are collected. These are coded according to the British National Formulary.
1.27.1 Visual impairment questions asked
Figure 4:19 LIDNS questions on long-standing illness, disability or infirmity
Heal“Do have any long-standing illness, disability or infirmity? By long-standing I mean an illness that you have has had over a period of time or that is likely to affect you over a period of time.”1 Yes2 No
HealT (ASK IF (Heal = Yes))“What is the matter with you?”SPECIFY
Limit
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 79
“Does this illness or disability (Do these illnesses or disabilities) limit your activities in any way?”1 Yes2 No
LimitShp (ASK IF (Limit = Yes))“Does this illness or disability (Do these illnesses or disabilities) limit you or prevent you from shopping?”1 Limits2 Prevents3 Neither
LShpHow (ASK IF ((LimitShp = Limits) OR (LimitShp = Prevents)))“Can you tell me how you are limited/prevented from shopping?INTERVIEWER: CODE ALL THAT APPLY”1 Difficulties with walking2 Problems with sight3 Cannot carry (heavy) shopping4 Gets tired easily5 Other difficulties
LimiPrep“Does this illness or disability (Do these illnesses or disabilities) limit you or prevent you from preparing food?”1 Limits2 Prevents3 Neither
LPrepHow (ASK IF ((LimiPrep = Limits) OR (LimiPrep = Prevents)))“Can you tell me how you are limited/prevented from preparing food?INTERVIEWER: CODE ALL THAT APPLY”1 Difficulties with hands (eg. chopping, peeling, lifting)2 Difficulties with walking3 Difficulties with standing4 Problems with sight5 Chronic ill-health (e.g. MS, depression)6 Gets tired easily7 Other difficulties
1.27.2 Visual impairment prevalence estimates What is interesting about the LIDNS questions is that they allow a
prevalence of the impact of impairment on ability to undertake tasks. 1.5%
of people in low income households reported that problems with their
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 80
eyesight limited their ability to do food shopping, and 1% of people said it
impacted on their ability to prepare food.
1.27.3 Methodological issues Coding of reason for medications only included heart problem or
high blood pressure.
BNF codes not labelled.
1.27.4 Study contacts and further informationBeverley Bates and Caireen Roberts, National Diet and Nutrition Survey
directors, NatCen.
http://www.esds.ac.uk/findingData/snDescription.asp?sn=5808
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 81
1.28 National Diet and Nutrition Survey (NDNS) 2008-9NDNS is a survey of the food consumption, nutrient intakes and nutritional
status of people aged 1.5 years and older living in private households. The
survey is carried out in all four countries of the United Kingdom (UK) and is
designed to be representative of the UK population. The Food Standards
Agency (FSA) commissioned it, with a contribution to funding from the
Department of Health. The programme is carried out by a consortium of
three organisations: The National Centre for Social Research (NatCen),
MRC Human Nutrition Research (HNR), based in Cambridge and the
Department of Epidemiology and Public Health at University College
London Medical School (UCL). The Northern Ireland Statistics and
Research Agency (NISRA) carry out fieldwork in Northern Ireland.
Similarities to the LIDNS, but with variables updated and based on a
sample drawn from the whole population and not just low-income
households.
1.28.1 Visual impairment questions asked
1.28.2 Visual impairment prevalence estimates The archived dataset contains data for 1017 adults and children up to age
64. As for LIDNS, NDNS includes questions that allow a prevalence of the
impact of impairment on ability to undertake tasks: the impact that
problems with their eyesight had on their ability to do food shopping, or
prepare food. In an advance on the LIDNS questions, NDNS
disaggregated responses into whether the impairment ‘limits’ or ‘prevents’
the tasks.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 82
1.28.3 Methodological issues Coding of reason for medications only included heart problem or
high blood pressure.
BNF codes ARE labelled.
1.28.4 Study contacts and further informationBeverley Bates and Caireen Roberts, National Diet and Nutrition Survey
director and nutritionist, Health and Wellbeing Team, NatCen.
http://www.esds.ac.uk/findingData/snDescription.asp?sn=5808
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 83
1.29 Life Opportunities Survey (LOS) 2010While the Life Opportunities Survey (LOS) is a new large-scale survey of
disability, its sample is not restricted to disabled people. It is the first major
social survey in Great Britain to explore disability in terms of social barriers
to participation, rather than only measuring disability in terms of
impairments or health conditions. LOS is conducted by the Office for
National Statistics, on behalf of the Office for Disability Issues (ODI).
LOS is a longitudinal survey. This means it will track the experiences of
disabled people over time through key life stages. It compares the
experiences of people with and without impairments across a range of
areas, including education and training, employment, transport, leisure,
social and cultural activities, and social contact. LOS is able to produce a
variety of estimates based on different definitions of disability.
18,000 adults aged 16 and over were interviewed in 2009/2010. This was
the first half of wave one data collection. A full wave one report will be
published in Autumn 2011, and eventually the dataset will be made publicly
available for analysis.
1.29.1 Visual impairment questions asked The LOS questionnaire was developed using the International
Classification of Functioning, Disability and Health (ICF) as a model to
classify impairments. The impairment section of the questionnaire includes
a series of questions relating to any difficulties respondents experienced
across a wide range of functions, including seeing.
Respondents are asked if they experience any difficulty in a particular area
of functioning (e.g. seeing). Respondents then provide information across
each area about the severity of the difficulties they have in relation to
performing specific activities (ranging from no difficulty through mild,
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 84
moderate, severe and, for some areas, complete).
Finally they are asked how often, if at all, that the amount or kind of
activities that they can do are reduced or affected, detailing the frequency
with which their activities are limited (never, rarely, sometimes, often, and
always).
A respondent is defined as having an impairment if they indicated that they
experience either moderate, severe or complete difficulty within at least
one area of physical or mental functioning, and certain activities are limited
in any way as a result.
A similar set of impairment screener questions are used in the Northern
Ireland Survey of Activity Limitation and Disability (NISALD). The relevant
questions included in LOS are in Figure 4.20
Figure 4:20 LOS questions on sightIVision Do you have any difficulty seeing, or wear glasses or contact lenses?
(1) Yes
(2) No
SeeClo APPLIES IF: IVision = Yes SHOWCARD R1 (With your glasses or contact lenses) do you have any difficulty seeing
ordinary newsprint at arm’s length?
SHOWCARD
(1) No difficulty
(2) Mild difficulty
(3) Moderate difficulty
(4) Severe difficulty
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 85
(5) Cannot do
SeeDis APPLIES IF: IVision = Yes (With your glasses or contact lenses) do you have any difficulty clearly
seeing the face of someone across a room, that is from 4 metres or 12 feet
away?
SHOWCARD
(1) No difficulty
(2) Mild difficulty
(3) Moderate difficulty
(4) Severe difficulty
(5) Cannot do
SeeLim APPLIES IF: SeeDis >1 OR SeeClo > 1 How often does this limit the amount or kind of activities that you can do?
SHOWCARD
(1) Always
(2) Often
(3) Sometimes
(4) Rarely
(5) Never
LOS classifies a respondent as having a ‘visual impairment’ if:
They report having moderate, severe difficulties or complete lack of
function in regards to seeing at either SeeClo or SeeDis; AND,
They report that this difficulty limits their daily activities (i.e. SeeLim=
rarely, sometimes, often or always).
Prior to these questions, LOS also contains a question to capture whether
respondents have any long-term impairments or disabilities. Respondents
who answer yes to this question are asked an additional question on how
their impairment impedes their functioning.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 86
Figure 4:21 LOS questions on long-term impairments and disabilityHealthDo you have any long-standing physical or mental impairment, illness or disability? By 'long-standing' I mean anything that has affected you over a period of at least 12 months or that is likely to affect you over a period of at least 12 months. (1) Yes (2) No
DisDif APPLIES IF: Health = Yes Does this/Do these health problem(s) or disability(ies) mean that you have substantial difficulties with any of these areas of your life? Please read out the numbers from the card next to the ones which apply to you.
INTERVIEWER: Probe: Which others? (1) Mobility (moving about) (2) Lifting, carrying or moving objects (3) Manual dexterity (using your hands to carry out everyday tasks) (4) Continence (bladder & bowel control) (5) Communication (speech, hearing or eyesight) (6) Memory or ability to concentrate, learn or understand (7) Recognising when you are in physical danger (8) Your physical co-ordination (e.g. balance) (9) Other health problem or disability (10) None of these
The codeframe used at DisDef classifies respondents by broad types of
functional impairment. It does not have a specific code for problems with
vision as problems with eyesight are coded as problems with
‘Communication’. Therefore these questions cannot be used to estimate
prevalence of visual impairments specifically.
1.29.2 Visual impairment prevalence estimates
This section will report on the following:
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 87
1. The number of respondents who reported some difficulty with their
sight, or that they needed to wear glasses or contact lenses
(IVision=Yes).
2. The number of respondents who reported having some difficultly
seeing (close up or distance) with glasses on (SeeDis=2-5, or See=
2-5)
3. The number of respondents who fell into LOS’s definition of having a
visual impairment.
In total 67.1% of respondents reporting having difficulties with sight or
using glasses or contact lenses. Prevalence rates by age groups and sex
are shown in Tables 4.17 and 4.18.
Table 4:17 Prevalence of ‘difficulties with sight’ / uses glasses or contacts, by age
Age 16-19 20-29 30-39 40-49 50-59 60-69 70-79 80+ TOTAL% % % % % % % %
Difficulties with sight/
uses glasses or
contacts
28.3 37.0 41.7 60.1 89.0 92.7 91.8 92.6
Base 1097 2346 2757 3251 2939 2766 1870 993 18019
Table 4:18 Prevalence of ‘difficulties with sight’ / uses glasses or contacts, by sex
Sex Male Female Total% % %
Difficulties with sight/ uses glasses or contacts 63.5 70.3 67.1Base 8476 9543 18019
Respondents who reported having difficulties with their sight initially were
asked two follow-up questions on whether, with glasses, they had any
difficulties reading newspaper print or seeing a face across a room.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 88
In total 9.9% respondents reported having difficulties at seeing at these
follow-up questions. 4.1% of respondents reported they had at least mild
difficulties seeing a face across a room. 8.9% respondents reported having
at least mild difficulties reading a newspaper held at arms length.
Table 4:19 Prevalence of reporting difficulties in seeing things up close and at distance, by age
Age 16-19 20-29 30-39 40-49 50-59 60-69 70-79 80+ TOTAL% % % % % % % %
Difficulty reading a
newspaper2.7 3.6 4.0 7.7 11.3 10.2 14.1 25.1
Difficulty seeing a
face across a
room
1.5 2.3 1.5 2.7 3.6 4.9 7.5 15.3
Difficulties with either
of the above
3.3 4.7 4.6 8.3 12.1 11.5 16.0 26.8
Base 1097 2346 2757 3251 2939 2766 1870 993 18019
Table 4:20 Prevalence of reporting difficulties in seeing things up close and at distance, by sex
Sex Male Female Total% % %
Difficulty reading a newspaper 8.4 9.3 8.9Difficulty seeing a face across a room 3.6 4.4 4.1Difficulties with either of the above 9.2 10.5 9.9Base 8476 9543 18019
Finally, 3.3% of respondents met LOS’s definition of having a visual
impairment (that is, they rated themselves at having moderate (or worse)
difficulties seeing (either when looking at things close up or at distance)
and stated that this limited the activities they do.)
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 89
Prevalence rates of visual impairment using this definition are shown in
Tables 4.21 and 4.22, by age group and sex.
Table 4:21 Prevalence of visual impairment by age, using LOS definition
Age 16-19 20-29 30-39 40-49 50-59 60-69 70-79 80+ TOTAL% % % % % % % %
LOS definition of visual
impairment
0.5 1.2 1.2 2.4 3.6 3.2 6.0 15.0
Base 1097 2346 2757 3251 2939 2766 1870 993 18019
Table 4:22 Prevalence of visual impairment by sex, using LOS definition
Sex Male Female Total% % %
LOS definition of visual impairment
2.9 3.7 3.3
Base 8476 9543 18019
1.29.3 Methodological issues Inclusion of impaired function/limiting activities
Different definitions naturally yield results:
SeeDis and SeeClo ask respondents to rate their difficulties rather
than give a flat Y/N
LOS’s question on seeing a face across a room is clearer than WHS
Q- any room for comparison.
Compare VisionI with APMS- BOTH include PROBLEMS CORRECT
BY SIGHT BUT VERY DIFFERENT RESULTS.
No information collected on type of condition.
Collects information of types of impairment and severity.
Also asks question on disability- some respondents classified by
LOS as having a visual impairment did not classify themselves as
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 90
having a disability at ‘Health’. This indicates that even moderately
severe visual problems ones that impact on activities are not
necessarily considered as disabilities: the disability approach to
capturing visual impairments could lead to underestimates when
respondents are routed by these questions.
1.29.4 Study contacts and further informationJoanna Bulman and Ian O’Sullivan, Life Opportunities Survey (LOS), ONS
http://www.statistics.gov.uk/statbase/Product.asp?vlnk=15386
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 91
1.30 Understanding Society 2010/11
Understanding Society is a longitudinal survey of the socio-economic
circumstances and attitudes of 100,000 people in 40,000 British
households. It is funded by the Economic and Social Research Council
(ESRC), and run by the Institute for Social and Economic Research (ISER)
with fieldwork undertaken by NatCen. The sample is drawn from the whole
population, and being longitudinal it will yield data for examining people’s
longer term occupational trajectories; their health and well-being, financial
circumstances and personal relationships.
It has an interdisciplinary focus. The study will capture biomedical data on
20,000 participants and place this alongside rich social histories, helping
us weigh the extent to which people's environment influences their health.
So far only the wave 1 year 1 data is on the archive, and for the general
population sample only (so no year 2 data and no ethnic minority boost
data yet). Responses collected from proxy respondents have been
excluded from this analysis.
1.30.1 Visual impairment questions asked
Figure 4:22 Understanding Society questions HEALTHDo you have any long-standing physical or mental impairment, illness or disability? By 'long-standing' I mean anything that has troubled you over a period of at least 12 months or that is likely to trouble you over a period of at least 12 months.1. Yes2. No
DisDif {IF Health = 1}Does this/Do these health problem(s) or disability(ies) mean that you have substantial difficulties with any of these areas of your life? INTERVIEWER: Probe: Which others?
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 92
CODE ALL THAT APPLY1. Mobility (moving around at home and walking)2. Lifting, carrying or moving objects3. Manual dexterity (using your hands to carry out everyday tasks)4. Continence (bladder and bowel control)5. Hearing (apart from using a standard hearing aid)6. Sight (apart from wearing standard glasses)7. Communication or speech problems8. Memory or ability to concentrate, learn or understand9. Recognising when you are in physical danger10. Your physical co-ordination (e.g. balance)11. Difficulties with own personal care (e.g. getting dressed, taking a bath or shower)12. Other health problem or disability96. None of these
1.30.2 Visual impairment prevalence estimates In total, 3.2% of respondents reported having substantial difficulties with their sight at DisDif. Prevalence rates of respondents reporting difficulties with their sight as are shown, by age groups and sex, in Tables 4.23 and 4.24.
Table 4:23 Prevalence of respondents reporting difficulties with sight by age group in Understanding Society
Age 16 -19 20 -29 30 -39 40 -49 50 -59 60 -69 70 -79 80+ TOTAL% % % % % % % %
Difficulties with sight at DisDif
0.6 0.8 1.4 1.8 3.1 4.8 7.3 14.1
Base 1324 3179 3865 4166 3529 3227 1979 962 22231
Table 4:24 Prevalence of Prevalence of respondents reporting difficulties with sight by sex in Understanding Society
Sex Male Female Total% % %
Difficulties with sight at DisDif 3.0 3.3 3.2Base 9692 12539 22231
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 93
1.30.3 Methodological issues Rely on routing from a disability question.
Asked for ‘substantial’ difficulties- not clear what this means.
Unlike HSE/ SHeS provides a prompted list of types of impairments
related to capacity instead an open question on condition. (Does not
appear to influence prevalence estimates).
Specific instruction to exclude glasses.
1.30.4 Study contacts and further informationAnne Connely and Richard Boreham, NatCen.
http://www.understandingsociety.org.uk/
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 94
4 Comparisons between surveysThe aim of this section is to compare how questions varied between
surveys and the influence this had on the profile of visual impairment
produced. It will do this by considering the:
1) five broad types of measure identified, and
2) varying inclusion and exclusion criteria applied to each question.
Throughout this section results from different surveys will be compared and
implications for data users discussed.
1.31Types of measures identifiedOverall the review found five main types of measure were being used to
collect data on visual impairment in national social surveys. These were:
1. Questions on disability and health conditions (with eye
conditions and visual impairment captured only as a follow-up
question about ‘type of disability’)
2. Questions about quality of sight and seeing (such as ‘do you
have any difficulties seeing?’).
3. Direct questions about the presence of specific ocular conditions
4. Questions on visual capability in particular contexts (whether
respondents have any difficulties seeing specific things under certain
conditions, for example the face of friend across the street).
5. Questions that ask respondent to rate their overall vision on a scale (for example, ranging from excellent to poor).
These different question types, including their strengths and weaknesses,
are discussed in more detail in the following sections.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 95
1.31.1 Questions on disability and health conditions
The most common form of survey data found on visual impairment was
collected using items that ask about the presence of a range of ‘disabilities’
and ‘health conditions’. These questions were typically found as part of a
‘general health’ module within the questionnaire. Within this category there
were three separate formats the question could take:
1) A routed question with an open follow-up: Respondents were first
asked if they had a health condition or disability. Only those who answered
‘yes’ were routed to an open follow-up question on what type of health
condition they had. This approach was used in HSE, SHeS, WHS, NDNS
and the FRS disability follow-up.
2) A routed question with a prompted list to follow-up. Respondents
were first asked if they had a health condition or disability. Only those who
answered ‘yes’ were then asked a closed follow-up question where they
had to pick types of impairment from a prompted list of answer categories.
This approach was used in LOS, Understanding Society, FRS, Living in
Wales and FACs.
3) A single prompted list. Respondents were asked a single question on
whether they had any of the ‘health conditions’ shown on a card. This
approach was only used in APMS.
A comparison of the overall prevalence of ‘visual impairment’ derived using
the questions in six of the surveys is shown in Figure 5.1. FRS, FRS
disability survey, FACs, and NDNS were excluded because they are not
directly comparable (due to sample composition, and issues with question
wording and sample-size).
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 96
Figure 5:23 Prevalence rates of visual impairment in general population surveys using disability questions
02468
101214161820
1
Survey
% V
isua
l im
pairm
ent
HSE: Y/N with openfollow-up
SHS: Y/N with openfollow-up
WHS: Y/N with openfollow-up
Living in Wales: Y/Nwith prompted follow-up
Understanding Society:Y/N with promptedfollow-upAPMS: Prompted list
A question that does not rely on routing (that is, a question that is asked of
the whole sample) generates a higher reporting of visual impairment. This
is because respondents who do not consider a problem with their eyesight
to be a ‘disability’ or ‘health condition’ (precise wording of the filter question
varies between surveys) would not be asked the follow-up questions that
are used to identify presence of visual impairment. This could lead to
survey data under-estimating the prevalence of visual impairment.
Conversely, it could also be that reports of mild or correctable visual
impairment are appropriately screened out with the use of a filter question.
APMS was the only survey to use a single prompted list asked of the whole
sample, rather than a routed approach. The Figure 5.1 shows that a much
higher proportion of respondents reported having a visual impairment in
APMS than in the other surveys (17.9%). However, it is likely that this
difference is mainly attributable to another difference in measurement. That
is, in APMS respondents were prompted to include problems corrected by
glasses or contact lenses. All of the other surveys either asked
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 97
respondents to exclude problems entirely corrected for by low vision aids
(often ‘glasses or contacts lenses’ is the wording used) or have no
inclusion instructions in this area.
In general it is unclear the extent to which variation in rate of visual
impairment between surveys is due to variations in question framing or to
the different inclusion and exclusion criteria applied (see section X.X). This
could be tested with split run experiments built into a survey design where
only one aspect of the question format is changed and other aspects kept
constant.
Open questions and ICD codingHSE, SHeS and WHS all adopt a similar approach to collecting information
on health conditions and impairments (that is, they use a routed question
with an open follow-up). Verbatim responsens to the open questions were
coded using the World Health Organisation’s International Classification of
Disease (ICD42) code frame.
It was beyond the scope of this scoping review to examine the original
verbatim responses (which will be a mix of symptoms and conditions) and
how these were assigned to ICD codes. This level of detail is not archived
in the UK Data Archive3, but is held securely by survey organisations like
NatCen. HSE coder instructions state conditions like colour blindness and
‘lazy eye’ should be included in the codes relating to visual impairment.
This may not be appropriate, depending on measurement aims.
HSE and SHeS show a similar prevalence of visual impairment using this
method (2.2%-2.3%). However, in WHS a smaller proportion of
respondents reported a visual impairment (0.7%). The lower incidence of
visual impairment could be due to several factors:
3 This is because they could potentially lead to the respondent being identifiable.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 98
Respondents are instructed to provide their main condition only in
WHS. Respondents who have multiple conditions may not consider
a visual impairment to be their main condition. Respondents may be
less likely to mention visual impairments if they are considered less
acute or are considered to be a secondary outcome.
In WHS respondents are only asked to include impairments that
‘limit daily activities or the work they can do.’ Respondents may not
feel that their visual impairment limits their activities.
WHS is a paper self-completion, so visually impaired respondents
may well be less likely to take part.
It is not possible to definitively state which of the above (if any) is the main
factor responsible for the discrepancy between survey results, it is likely
that they all contribute to the low prevalence of visual impairment identified
on WHS.
NDNS (excluded from the comparison analysis due to its small sample
size) uses a similar question approach to that used in HSE and SHeS,
although like WHS it only collects details of the first disability or health
condition mentioned. In NDNS no respondents recorded having a visual
impairment, respondents may have mentioned visual impairments but this
information was never processed as it was not coded as the primary
condition. This suggests that where open follow-up questions are used, it is
important that respondents are able to report multiple conditions and that
all conditions should be coded for analysis.
Prompted lists on functioningBoth FRS and LOS used a prompted list that aimed to establish what
areas of functioning were impaired, rather than what types of conditions
respondents had. The prompted lists, used in both FRS and LOS, are
provided below.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 99
Survey: FRS{If Health=Yes}DisDif Does this/Do these health problem(s) or disability(ies) mean that you have substantial difficulties with any of these areas of your life? Please read out the numbers from the card next to the ones which apply to you. 1: Mobility (moving about) 2: Lifting, carrying or moving objects 3: Manual dexterity (using your hands to carry out everyday tasks) 4: Continence (bladder and bowel control) 5: Communication (speech, hearing or eyesight) 6: Memory or ability to concentrate, learn or understand 7: Recognising when you are in physical danger 8: Your physical co-ordination (e.g. balance) 9: Other health problem or disability 10: None of these
Survey: LOS{Health = Yes}DisDif Does this/Do these health problem(s) or disability(ies) mean that you have substantial difficulties with any of these areas of your life? Please read out the numbers from the card next to the ones which apply to you. (1) Mobility (moving about) (2) Lifting, carrying or moving objects (3) Manual dexterity (using your hands to carry out everyday tasks) (4) Continence (bladder & bowel control) (5) Communication (speech, hearing or eyesight) (6) Memory or ability to concentrate, learn or understand (7) Recognising when you are in physical danger (8) Your physical co-ordination (e.g. balance) (9) Other health problem or disability (10) None of these
Due to the categories used, the functioning questions used in FRS and
LOS are not able to distinguish issues related to vision from those of other
‘communication’ ‘health problems or disabilities’ (although LOS does
include separate questions about vision elsewhere). A more suitable list of
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 100
functioning impairments was used in Understanding Society, where vision
is specifically mentioned as an area of functioning.
Inconsistent use of terms: ‘disability’, ‘infirmity’, ‘condition’ The word ‘disability’ is used in many survey questions in a way that is not
informed by a social model understanding of the term. We have used the
word in this review – often, but not always, in quote marks – because it is
part of the common terminology used in general health survey questions.
The questions that collate data on visual impairment use an array of
imprecisely understood words: disability, illness, infirmity, health-problem,
complaint, and health condition appear to be used interchangeably.
Likewise, questions vary in terms of how they define what constitutes a
‘long term’ and ‘long-standing’ condition. Figure 5.2 shows various different
wordings that were used in different surveys.
Figure 5:2 Terms used in questions that collect data on visual impairmentSurveys: HSE 2007 /FACs 2007 /Living in Wales 2008 / LIDNS Do you have any long-standing illness, disability or infirmity? By long-standing I mean anything that has troubled you over a period of time, or that is likely to affect you over a period of time?1 Yes2 No
Survey: SHeS 2008Do you have a long-standing physical or mental condition or disability that has troubled you for at least 12 months, or that is likely to affect you for at least 12 months?1. Yes2. No
Survey: WHS 2007Do you have a long-term illness, health problem or disability which limits your daily activities or the work you can do? (Include problems which are due to old age).
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 101
1. Yes2. No
Survey: FRS 2008Do you have any long term health problems or complaints which affectyour everyday activities?1.Yes 2.No
Survey: Understanding Society W1Do you have any long-standing physical or mental impairment, illness or disability? By 'long-standing' I mean anything that has troubled you over a period of at least 12 months or that is likely to trouble you over a period of at least 12 months.1.Yes 2.No
A key issue is whether the wording used influences whether or not
respondents decide to include problems with sight. It is currently not clear
which phrasing, if any, is preferable. Cognitive testing work examines
respondent understanding of survey questions and the thought processes
they go through when deciding how to respond. Such pilot work, using
‘general health’ filter questions with respondents with a range of different
types of visual impairment, would be key to bringing insight to this.
1.31.2 Questions on visual capabilityThe review identified four national social surveys that asked questions
about visual capability. These were:
WHS (one question on being able to see faces at distance)
FRS Disability (a series of questions on being able to see things up
close and at distance)
LOS (two questions, where respondents state to what extent they have
difficulties seeing things close up or at a distance).
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 102
NDNS (two questions that looked at whether a visual impairment limited
respondents’ ability to go shopping or to prepare food).
These questions are shown in the box below.
Survey: WHSSEEIs your eyesight good enough to see the face of someone across a room? (Using glasses or contact lenses if you usually wear them)YesYes with difficultyNo
Survey: FRS DisabilitySeeFrnd(Wearing glasses or lenses... ) Do you have difficulty recognising a friend across the road?Yes No
Reading(Wearing glasses or lenses…) Do you have difficulty reading ordinary newspaper print?Yes No
Windows (APPLIES IF SeeFrnd=Yes or Reading=Yes)Can I check, (wearing glasses or lenses...) in a room during daytime,can you tell by the light where the windows are?Yes No
Shape (APPLIES IF Windows=Yes)(Wearing glasses or lenses...) Can you see the shapes of the furniture in this room?Yes No
RecFace (APPLIES IF Shape=l)(Wearing glasses or lenses…)
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 103
Can you see well enough to recognise a friend if you get close to his or her face?Yes No
ArmLeng (APPLIES IF RecFace~l)(Wearing glasses or lenses... ) Can you see well enough to recognise a friend who is an arms length away?Yes No
Headline (Wearing glasses or lenses... )Can you see well enough to read a newspaper headline?Yes No
LargePrt (APPLIES IF Headline=l)(Wearing glasses or lenses... )Can you see well enough to read a large print book?Yes No
Room (APPLIES IF LargePrt=l)(Wearing glasses or lenses… )Can you see well enough to recognise a friend across the room?Yes No
Survey: LOSSeeClo (With your glasses or contact lenses) do you have any difficulty seeing ordinary newsprint at arm’s length? (1) No difficulty (2) Mild difficulty (3) Moderate difficulty (4) Severe difficulty (5) Cannot do
SeeDis
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 104
(With your glasses or contact lenses) do you have any difficulty clearly seeing the face of someone across a room, that is from 4 metres or 12 feet away? (1) No difficulty (2) Mild difficulty (3) Moderate difficulty (4) Severe difficulty (5) Cannot do
Due to the fact that the questions differ (and that the FRS Disability survey
comprised a very different sample), it is not possible to directly compare
the results from these four surveys. However, it is possible that the FRS
Disability questions and the LOS questions may be more useful as they:
1) Contain fewer ambiguities than the WHS question
2) Collect a greater range of information (capturing both seeing
things close up and seeing things at a distance)
3) Collect details to gauge the severity of the limitations described.
In WHS more respondents reported having difficulty seeing using this
approach than with the open question on disability type (see Section 4.3).
One overarching question on ‘difficulty seeing’ or use of ‘glasses or contact
lenses’ was identified. This question was in LOS and is shown below.
IVision Do you have any difficulty seeing, or wear glasses or contact lenses?
1. Yes
2. No
The proportion of respondents who reported difficulty in seeing at this
question was the highest across all the surveys reviewed (67.1%). This is
likely to be due to the fact respondents are directly asked whether they
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 105
wear glasses or contact lenses. Furthermore, the context of glasses use is
not specified and implies inclusion of occasional use of LVAs such as for
reading, computer use or the cinema. In contrast, in the same survey only
9.9% of respondents reported difficulty seeing things using the visual
capability measures (see Section 4.12).
Interestingly, the general question in LOS produced a higher prevalence
rate than the APMS disability question that provided a prompted list of
health conditions including the item ‘cataracts/eyesight problems (even if
corrected with glasses or contacts).’ For the APMS question only 17.6% or
respondents reported having problems (even if corrected with glasses or
contacts) in the last 12 months. This suggests that the use of the word
‘problems’ can alter respondents’ understanding of the question.
Respondents may be more likely to report the fact they wear glasses than
that they have a problem with their eyesight that is corrected by glasses.
1.31.3 Questions on specific ocular conditionsOnly one of the surveys reviewed, ELSA, contained measures that
captured specific ocular conditions. This included specific measures on
whether respondents had been diagnosed with cataracts, macular
degeneration, glaucoma, and diabetic eye disease.
ELSA only collects data from people aged 50 and over. However, both
HSE and SHeS contain sufficient numbers of older respondents for
comparisons to be made with the data collected at ELSA. Table 5.1 and
Figure 5.3 show how visual impairment measures vary among people aged
50 and over (using either an open question on disability (HSE, SHeS) or
specific prompts for ocular conditions (ELSA)).
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 106
Table 5:25 Visual impairment measures among older people, by survey and age groupSurvey Visual impairment measures 50-59 60-69 70-79 80-89HSE 2007 ICD code 9 or 10 reported at
‘IllsTxt’ 1.2% 2.3% 4.8% 11.4%Base 1094 1077 727 333
SHeS 2008 ICD code 9 or 10 reported at ‘IllsM’ 1.6% 2.8% 4.2% 9.9%Base 1153 1095 783 332
ELSA W4 Glaucoma, Macular degeneration, diabetic eye
disease or cataracts reported at ‘Heop’ 6.6% 15.7% 34.3% 41.6%
Base 2899 3506 2358 982
Figure 5:24 Prevalence of visual impairment, by survey and age group
Within equivalent age bands reports of ocular conditions are much higher
in ELSA then in HSE or SHeS (despite the fact HSE and SHeS have
broader inclusion criteria, as any type of eye condition could have been
reported). This suggests that respondents are much more likely to report
the presence of ocular conditions when specifically asked about it. In HSE
and SHeS rates of visual impairment are likely to be underestimates, as
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 107
the measures are not specific enough. Respondents are more likely to
report ocular conditions if they are prompted by a specific example, rather
then asking about ‘illness,’ ‘disability’, ‘infirmity’, or ‘health conditions’ in
general.
Subjective data collected during the interviews can be seen as
unprompted, prompted or observed measures. xxxix The latter is based on
interviewer observations, such as the interviewer coding the reason that a
self-completion module was not completed was because of sight problems.
This ties in with reporting of findings from Network 1000, which
identified the most useful measure in one set of analyses as being a
prompted question that directly asked the participant about difficulties that
they have with seeing.
1.31.4 Questions on self-rated eyesightOne question was identified where respondents were asked to rate their
own eyesight overall (on a scale from excellent to poor). The question was
on ELSA and therefore not asked of the general population. As discussed
in Section 4.5, it is very interesting to note that the majority of people who
reported having an ocular condition at ELSA still rated their eyesight highly
(39.3% of people with an ocular condition rated their eyesight as ‘good’,
21.9% rated their eyesight as ‘very good’, and 7.8% rated their eyesight as
‘excellent’). This suggests that a measure of self-rated eyesight is
understood by respondents to mean something quite distinct from
presence of an ocular condition. Given the two questions are asking
different things, one should never be used as a substitute for the other. For
example, a question on self-rated eyesight should not be used as a proxy
measure of the presence of ocular conditions.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 108
1.32 Inclusion and exclusion criteriaIn addition to different question wordings and formats, there was also
variation in terms of inclusion and exclusion criteria. The two main areas of
related to:
Use of low vision aids
Whether conditions ‘limit day to day activities’.
1.32.1 Use of low vision aids (LVAs)There was variation in the instructions to respondents on whether or not
low vision aids should be taken account of. Some questions stated to:
Exclude eye problems that were fully corrected by ‘glasses and
contact lenses’
Include problems corrected by glasses
Some gave no inclusion criteria in relation to this.
APMS, was the only one to indicate that problems with eyes that were
correctable should be included. As discussed in Section 5.1, the
prevalence of reporting visual impairment was far higher for this survey
(17.6%) than for the HSE and SHeS (2% to 3%). Low vision aids were
almost exclusively defined as ‘glasses or contact lenses’, with other types
not mentioned. Where surveys did not indicate whether or not correctable
sight loss should be included, it is hard to know how respondents
interpreted the question. Furthermore, where the question was one to be
read out by the survey interviewer (rather than administered by self-
completion) the reference to low vision aids may not in practice have been
read out at all, especially if the respondent was not clearly wearing glasses
at the time of the interview. The reference to ‘glasses and contact lenses’
was often given in the question text in parenthesis, which indicates to the
interviewer that it only needs to be read out ‘if necessary’.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 109
1.32.2 Whether conditions are ‘limiting’As also discussed in Section 5.1, WHS data produce a lower prevalence of
visual impairment (0.5%) than HSE and SHeS despite using the same ICD
code frame. One of the factors impacting on this is likely to be the fact that
WHS specifies only including conditions that ‘limit your daily activities or
the work you can do.’ The difference in rate however is likely to also result
from the fact that the question specified inclusion of ‘one illness only.’
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 110
5 Conclusions Most social surveys in Britain do not collect information on visual
impairment. Among those that do, there is great variation in the questions
used. They employ a range of different measurement constructs (including
type of impairment or condition, capability and function, symptoms, and
general self-rating). Different questions generate very different rates of
‘visual impairment’.xl Despite this, we (and Robertson and Emerson) find a
reassuring amount of consistency where similar questions have been
used.xli
With greater consistency in questions used on different surveys it would be
easier to combine surveys to produce large samples of visually impaired
people for analysis. However - and more importantly - many of these
questions are likely to be very poor predictors of visual impairment as
diagnosed by means of more objective measures.
There are some plans to reduce the extent of variation in disability
questions used and to improve their validity. The Office of Disability Issues
(ODI) has been involved in an on-going project with ONS to develop a
harmonised suite of disability questions to measure the prevalence of
disability as defined by the Equality Act. The questions may well present
an improvement in how ‘disability’ is measured in surveys, and may
address some of the inconsistency there is in the terminology used (with
illness, infirmity, complaint, impairment and disability widely used
xl Mont D. (2007) Measuring Disability Prevalence. Washington DC. USA:
The World Bank.xli Robertson J and Emerson E. (2010). Estimating the number of people
with co-occurring vision and hearing impairments in the UK. Centre for
Disability Research.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 111
interchangeably). However, it does not seem to address many of the
problems that this review has identified in the measurement of visual
impairment.
Visual impairment measurement on social surveys suffers from a lack of
priority accorded the subject by ‘mainstream’ research commissioners and
survey managers. It is seen as a specialist, rather than generalist, subject
area. Further, mainstream survey coverage of the subject is unlikely to be
able to provide the level of accuracy and detail that many users of this data
might require, such as an accurate assessment of visual acuity. Quite
considerable time and training would be required to include objective
measures on surveys. Piloting of such measures (for example on the
Better Design Survey) have not yet been fully successful.
An ambitious recommendation would be to examine the suitability of a two-
phase survey design, where brief screening questions are included on a
national social survey, followed by a phase two clinican administered
assessment with those screening positive. Such an approach is used
widely in health research, for example on studies of dental health and
psychiatric morbidity.
There is great competition for space on national general population
surveys. In the current climate, with several national survey programmes
having been suspended or their questionnaires shortened to save costs,
this problem is compounded. Much research commissioning has moved
away from funding the collection of primary data and towards secondary
analysis of existing datasets. However, very specific data on visual
impairment exist that are currently hard to access. Details on conditions
are often either a) not collected, b) not fully coded, c) over aggregated, d)
not reported on, or e) not even archived. We recommend a review of
archival practice to encourage the secondary analysis of survey data on
this topic. There is a movement towards fewer variables being archived
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 112
due to the data security risks of disclosure resulting from variables being
archived in combination. However, a common sense approach is required
to ensure that these risks are not overstated.
‘Wellbeing’ is currently one of the few ‘growth areas’ in social research.
Demonstrating a strong link between visual impairment and wellbeing will
be key to admitting this topic to the mainstream research and policy
agenda, alongside publicising the fact of the growing proportion of the
population who will be affected in the coming decades.
The key methodological limitations to existing questions vary between
surveys, but include:
The use of a ‘disability’ filter question
The collection of one primary condition
Inconsistency and ambiguity around inclusion LVAs /correctable
sight problems
Restriction to ‘limiting’ conditions
Lack of respondent awareness about diagnoses and causes
Lack of clarity about the distinction between conditions, symptoms,
and functional impairments.
With the wider (but very much incomplete) move across social research
and policy from a medical to a social model of disability, information on
conditions will be collected less and less. But the focus may shift towards
examining barriers that are amenable to policy, and to research that better
addresses social equality issues.
A key issue to communicate to the ‘mainstream’ survey research world is
what is the primary research need. If it to identify the population of people
who’s day-to-day lives are affected by sight loss, then the key
recommendation is to include a non-filtered question that includes a
specific prompt. This should be administered face to face rather than in a
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self-completion. If the key issue is to identify what proportion of the
population has particular ocular conditions or to understand the causes of
sight problems, then it may be that administrative data sources are
preferable. Great improvements are underway in the collection,
management and analysis of administrative datasets, including information
on medications and diagnoses. There is great scope to extend the analysis
of survey-collected information on medication use, and, furthermore, the
analysis of linked survey and administrative data sources such as hospital
episode and mortality statistics.
Administrative data sources, however, tell us very little about the lives of
people: their families, social networks, wellbeing, employment and more.
And it is only general population samples that enable people with sight loss
to be compared with the rest of the population. Survey datasets are also
better than administrative sources for examination of trends, because the
criteria influencing inclusion in administrative sources have been changing.
Better quality general population survey data on visual impairment is
therefore crucial.
We hope that this scoping review will be useful to survey designers and managers; data coders; research analysts; and people in organisations responsible for commissioning or provision of services. This is a draft report and we welcome comments, suggestions and revisions. Please let us know if you would like to take part in a discussion of the findings and in formulating the recommendations.
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Appendix A Summary of surveys
Summary table of reviewed surveys, sample and questions.Survey Question type Cover Methods Prev’
%Longstanding ‘illness, disability or infirmity’
Prompts specific ocular conditions
Visual capability
Self-rated quality of eyesight
e.g. Do you have any longstanding illness, disability, or infirmity of any kind?
Type of long-standing illness question
e.g. Has a doctor or optician ever told you that you have cataracts?
e.g. Do you have difficulty reading ordinary newspaper print?
e.g. Is your eyesight ..1.excellent2 very good3 good4 fair5 or poor?
HSE Y/N with open follow-up on specific condition
None Conditions coded with ICD code-frame
2.2%
SHeS Y/N with open follow-up on specific condition
None Conditions coded with ICD code-frame
2.3%
WHS Excludes problems corrected by glasses
Paper self-completion
5.6%4
4 Seeing things at distance only
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Y/N with open follow-up on specific condition
Only includes conditions that limit activities
Asks for main condition only
0.7%
APMS Prompted list of condition type (e.g. eyesight problems)
Includes conditions corrected by glasses
17.6%
ELSA None Sample is aged 50+
20.5%
Rating eyesight whilst wearing glasses
Sample is aged 50+
3.6%5
FACs Y/N with prompted list to follow-up (e.g. Difficulty in seeing)
None Sample of parents in receipt of child benefits
0.6%
FRS Y/N with prompted follow-up on how functioning is
None Function measures do not specifically code problems with vision
N/A
5 Rate eyesight as ‘poor’ or state they are registered blind.
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impaired
FRS- Disability follow up
Y/N with open follow-up on specific condition
Only includes conditions that limit activities
Sample disabled or aged 75+
6.8%
Excludes problems corrected by glasses
Sample disabled or aged 75+
18.4%6
Living in Wales
Y/N Prompted list of condition type (e.g. vision)
None 8.6%CHECK
NDNS Y/N with open follow-up on specific condition
None Conditions coded with ICD code-frame. Only first condition mentioned coded.
0.0%
Small sample: n=459
Only includes conditions that limit activities
Captures whether shopping/ food prep is impaired due to ‘problems with sight’
0.2%
Small sample, n=459
LOS Y/N With
None Function measures
N/A
6 Either difficulty seeing things at a distance or up close
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 117
prompted follow-up on how functioning is impaired.
do not specifically code problems with vision
Excludes problems corrected by glasses
Rs asked to rate difficulty on a 5-point verbal scale.
9.9 7
As above but only includes moderate difficulties that limit activities
Rs asked to rate difficulty on a 5-point verbal scale.
3.3
Understanding Society
Y/N with prompted list on how functioning is impaired
Excludes problems corrected by glasses.
Function measures include code on ‘sight’
3.2
7 Mild difficulty or greater seeing things close up or at distance.
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Appendix B Project team
Project teamNatCen is the UK’s largest independent social research institute, it is non-
profit making and with charitable status. The authors are part of the Health
and Wellbeing Team and the Research Methods Hub at NatCen. NatCen
conducts and analyses many of the key UK national social surveys, and
this study has benefited from the direct input of many of the surveys
managers.xlii
Project advisorsThe project team are survey methodologists and data analysts with an
specific interest in health, disability and wellbeing. However, we are not
experts in visual impairment. We have therefore drawn on experts in the
field (in academia, the charitable sector and in Government departments
and agencies). See Section 1.5 for a list of some of the people who have
contributed.
xlii See http://www.natcen.ac.uk/natcen/pages/or_health.htm.
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Appendix C Suggested further work
SummaryThere are a number of ways in which this initial scoping review could be
developed and extended:
C1 - Include administrative and international data sources, as well as
coverage of child populations.
C2 - Conduct cognitive development work with people with a wide
range of types of visual impairment to explore how they interpret
existing survey questions (including the new harmonised set of
disability questions) and to inform the development of improved
questions and methodological administration.
C3 - Run a split run experiment on a national social survey sample to
test the impact of specific aspects of ‘disability’ question wording.
C4 - Provide a case study of how a visual impairment variable is
constructed, in theory and in ‘warts and all’ practice, and construct an
improved derived variable by recoding raw data from 10,000 Health
Survey for England (HSE) respondents.
C5 - Develop practical guidance on improved question administration,
interviewer instructions, editing guidance and raw data codification,
developed through dialogue with interviewers, data editors and coders,
survey methodologists, survey commissioners and clinical researchers.
C6 - Conduct secondary analyses of the Health Survey for England
(HSE) using descriptive cross-tabulations, multivariate logistic
regression, and other statistical approaches in relation to trends over
the past 12 years, subgroups such as people of working age and
ethnic minorities, and social inclusion, participation and service use.
The available sample includes more than 100,000 people in the
general population..
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C7 - Review what further secondary analyses of HSE and other
existing data sources could cost effectively be performed, in particular
in relationship to linked HSE and hospital episode and mortality statistics.
C1 Extend the scope of the review
Include administrative data sources, such as HES and registration, and
identify international examples of best practices. Exclude the population
scope to include children. Focus on identifying and analysing the key
longitudinal data sources available on this topic.
C2 Cognitive development work with visually impaired peopleConduct cognitive development work with people with a wide range of
types of visual impairment to explore how they interpret existing survey
questions (including the new harmonised set of disability questions) and to
inform the development of improved questions and methodological
administration. Cognitive work is ideally place to examined how visually
impaired people actually understand the questions used.
C3 Run a split run experiment Run an experiment whereby a randomly allocated half of the sample are
given one version of a question wording, and the other half are given the
same question but different in only one aspect. The impact of that aspect
of the survey question can then be gauged.
C4 and C5 Developing the HSE coding of visual impairmentAs the primary source of community based prevalence of conditions, it
would be useful to examine the current process of capturing visual
impairment in the Health Survey for England (HSE), and to propose to the
survey team improvements to the future collection and codification of such
data. The question format used on HSE is standard to many other surveys,
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so lessons drawn would have wider relevance. Its codification is based on
ICD-10, although in practice data are collected by interviewers and coded
by coders and there is scope for improvement in both.
The present HSE coding approach does not distinguish between eye
pathology and other treatable forms of sight loss such as cataracts (see
Chapter 4 for the coding frame). It also includes a mix of symptoms and
diagnoses, which in part is a reflection of the fact that respondents often do
not know the name of the conditions that they have. Therefore, such work
would seek to generate clearer instructions for field interviewers, a more
useful coding scheme for data coders and practical guidance for research
analysts in interpreting such data.
It would also seek to review whether useful information could be drawn
from the data collected on the HSE nurse visit about all medications
currently taken by respondents. Information drawing on the medication
data could be combined with self-report data to create an additional
derived variable of visual impairment.
A piece of work of this kind would be undertaken alongside the HSE survey
team and would involve:
1) An examination of verbatim responses to questions about long
standing illness, disability or infirmity that are sight-related. This
would include exploring raw data generated from HSE 20078 by
deriving test data, identifying verbatim responses that are sight
related, and establishing how responses are coded using existing
methods and to what extent data it is being multi-coded, and
producing new derived variables of visual impairment based on
HSE 2007 data.
8 As this level of data (the raw verbatim responses provided by respondents and keyed into the laptop by the interviewer) is not publicly archived, we would need internal (NatCen) ethical approval to conduct such analyses, but do not anticipate difficulty in obtaining this.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 122
2) Drawing on wider expertise to review and help identify typologies of
conditions or symptoms or combinations of symptoms (based on
HSE data) that may be considered to constitute ‘visual impairment’.
Generate recommendations for revisions to the coding frame.
3) Revised coding and editing instructions of visual impairments could
be developed for use in future waves of HSE.
4) Produce a new derived variable, which could be used in future
analyses related to sight impairment.
5) Furthermore, the new coding scheme could be used to re-
categorise HSE sight related raw data from 1997 to 2007.
C6 and C7 Secondary analyses of HSE and other survey datasets: trends, subgroups and social inclusionResearch suggests that unregistered individuals with sight loss access
different levels of support and services compared with registered
individuals, and that their general experiences of independence, quality of
life, and community participation are likely to be different.xliii Furthermore,
many factors (other than severity) influence whether or not an individual
becomes registered, and these factors could change with time.xliv,xlv Trends
in the registration rate cannot therefore be relied on to reflect trends in
actual levels of sight loss in the population.
xliii Percival J and Hanson J. (2007) ‘I don’t want to live for the day any
more’: visually impaired people’s access to support, housing and
independence.’ British Journal of Visual Impairment. 25(1):51-67.xliv Bruce, I, Harrow, J and Obolenskaya, P. (2007) ‘Blind and partially
sighted people’s perceptions of their inclusion by family and friends’. British
Journal of Visual Impairment. 25(1): 68-85.xlv Johnson, MRD and Morjaria-Keval A. (2007) ‘Ethnicity, sight loss and
invisibility.’ British Journal of Visual Impairment, . 25(1): 21-31.
REVIEW OF VISUAL IMPAIRMENT SURVEY QUESTIONS 123
In a key piece of research funded by the Pocklington Trust, Gjonça and
Nazroo used survey data to profile visual impairment in England.xlvi Their
study covered older people only and reflected one snapshot in time. This
could be extended by using nationally representative survey data that:
covers the whole adult age range, and
has been collected continuously since 1997.
Secondary analysis could be undertaken of the combined HSE survey
series (using the existing HSE visual impairment variable, although this
could be reviewed if the work outlined above was undertaken). The
analysis could involve a sample of men and women with and without self-
assessed visual impairment generated by combining the HSE 1997 to
2007 datasets. This would provide not only a substantial sample of 2,671
adults aged 16 and over with self reported sight loss, who can be
compared with 107,351 people without sight loss, but also enable trends
over time to be considered by dividing the sample into survey years (see
Figure B1). By including the boost year samples (when older or minority
ethnic people were over-sampled) the number of people with a self-
reported visual impairment in the sample would be over 4,000.
Figure B1 Presence of self-reported visual impairment in adults aged 16+ (HSE core sample 1997-2007)
All adults aged 16+
Survey year
Sample sizeSelf-reported visual impairment Total sample size
N % N
HSE 1997 228 3 8,575HSE 1998 382 2 15,898HSE 1999 189 2 7,797
xlvi Gjonça, E and Nazroo, J. (2006) An investigation of the circumstances
of older people with sight loss: analysis of the English Longitudinal Study of
Ageing. Thomas Pocklington Trust Occasional Paper 9.
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HSE 2000 179 2 7,986HSE 2001 410 3 15,638HSE 2002 190 3 7,393HSE 2003 415 3 14,832HSE 2004 176 2 7,465HSE 2005 182 2 7,630HSE 2006 320 2 14,137HSE 2007 151 2 6,882Base 2,671 2 107,351
The analyses could also be run on working age adults, of whom 1,180 in
the dataset have a self-reported visual impairment (see Figure B2).
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Figure B2 Presence of self-reported visual impairment in adults of working age 16-65 (HSE sample 1997-2007)
Adults aged 16-65
Survey year
Sample sizeSelf-reported visual impairment Total sample size
N % N
HSE 1997 107 2 7,013HSE 1998 162 1 12,833HSE 1999 84 1 6,303HSE 2000 68 1 6,416HSE 2001 177 1 12,513HSE 2002 83 1 5,970HSE 2003 160 1 11,794HSE 2004 71 1 5,895HSE 2005 73 1 6,118HSE 2006 133 1 11,024HSE 2007 62 1 5,353Base 1,180 1 91,232
Trends in visual impairmentOne aspect of such research would be to examine trends in the prevalence
of visual impairment over time (1997 to 2007) in a representative sample of
non-institutionalised adults across the age range and of those of working
age (16-65) in England. The approach would be similar to that used by Lee
et al. in ‘Trends in Visual Acuity Impairment in US Adults’.xlvii Trends would
be run overall and for men and women separately, and there is scope to
look at trends within some subgroups (e.g. by looking at a rolling average).
Socio-demographic profile
xlvii Lee, DJ; Go´mez-Marı´n, O; Lam, B; et al. ‘Trends in Visual Acuity
Impairment in US Adults: The 1986-1995 National Health Interview Survey’
Arch. Ophthalmol: 122, Apr 2004.
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Descriptive cross tabulations could be used to identify the key patterns and
associations between visual impairment and socio-demographic indicators
(including age, sex, socio-economic status, household income, housing
tenure, employment status, being in receipt of benefits and living
arrangements). Ethnic origin could be included as HSE included large
boosts of minority ethnic groups in 1999 and 2004. Data would be
presented both observed and after age-standardisation,xlviii the latter to
enable comparison between people with and without visual impairment
while controlling for different age profiles of different groups. Observed
tabulations are important as they profile the population in an accessible
way and present population-based estimates of level of current need.
Factors associated with visual impairmentRegression analyses could be used to examine associations between
visual impairment and each characteristic, while controlling for all the other
characteristics in the model. So for example, we can see whether there is
an association between ethnicity and visual impairment, after controlling for
age, sex, and the other socio-economic variables in the model.
General health, health conditions and hearing lossSelf-reported general health status among adults with a visual impairment
could be compared with the rest of the general population sample. The
relationship between visual impairment and other physical and
psychosocial health indicators could also be examined, identifying levels of
co-morbidity with other impairments (including hearing loss and general
mental well-being) and the extent to which these limit individuals’ activities
in any way.
Service useDescribe the level and nature of service use among older people with a
visual impairment (including use of community services such as meals on xlviii Age-standardised estimates are used to enable groups to be compared
after adjustment for any differences in their age distributions.
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wheels and voluntary workers, use of home help, contact with GP, in and
out patient appointments and hospital stays, and local authority care),
compare with older people without a visual impairment, and describe
changes over time.xlix
Social inclusion and networksExplore some of the associations between visual impairment and
dimensions of social capital including social participation and networks as
measures of social inclusion. The quantity and quality of social interaction
are important components of social capital. We propose various strands of
analysis with this emphasis including perceived social support. Recent
research has investigated perceptions of social support among visually
impaired people and found that this group reported a lack of social
integration within the community compared to the general population (ref).
It would be possible to draw on this work and explore the associations
between visual impairment and levels of perceived social support from
family and friends. HSE also provides two different measures of social
networksl asked of older adults that include ‘contact with family’ and
‘contact with friends’. ‘Contact’ was defined as including how often they
met face to face and how often they spoke over the phone. The analysis
would aim to draw out the level and nature of contact among visually
impaired people, compared to the general population.
Further secondary analyses of HSE might include examining views of the
local environment and ease of access to local amenities among visually
impaired people and exploring postcode level characteristics of
respondents’ neighbourhoods as measured by the Index of Multiple
Deprivation.
xlix The health services questions were asked of adults aged 65 years and
over. HSE 2003 survey did not include this module. l Questions about the nature and level of contact received from family and
friends were asked in HSE 2005.
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Notes and References
xxxix Sue Pavey, Sarah Bodsworth, Graeme Douglas, Isabel Clare, and Liz
Hodges (2007) Secondary data analysis with a focus upon the needs of
older people with acquired hearing and sight loss: An analysis of the
‘Network 1000’ and ‘Cambridge’ datasets. Research Report prepared for
Thomas Pocklington Trust as part of the research project “Experiences of
people with both hearing and sight loss”.
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