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Myopia in Singapore: taking a public healthapproach

Benjamin Seet, Tien Yin Wong, Donald T H Tan, Seang Mei Saw, Vivian Balakrishnan,Lionel K H Lee, Arthur S M Lim

Myopia is a problem of public health concernin Singapore for three reasons. Firstly, theprevalence of myopia (more than 0.5 dioptres(D)) is one of the highest worldwide. Twentyper cent of Singapore children are myopic at 7years at the start of their primary education,1

with prevalence exceeding 70% upon complet-ing college education.24 Other populationbased studies showed myopia prevalence of15% in preschool 4 year old children,5 80% inmilitary conscripts,6 and nearly 40% in adultChinese aged 40 and older.7 This is 1.53times higher than similarly aged white or blackpopulations in the United States,810 andelsewhere.11 12

Secondly, a large proportion of Singapor-eans has high myopia (more than 6.0 D),which has been observed across the whole agespectrum.1 6 7 While the prevalence of highmyopia is less than 2% in most Western popu-lations,10 11 approximately 10% of Singaporeadults have the condition.6 7

Thirdly, available data suggest that bothprevalence and severity of myopia have in-creased significantly over the past two decades.Based on serial cross sectional data from theSingapore Armed Forces, myopia prevalencein military conscripts has increased from 26%in the late 1970s, to 43% in the 1980s, 66% inthe mid 1990s, and 83% by the late 1990s.6 13 14

This is accompanied by a twofold rise in the

proportion with myopia worse than 8 D, from2% to 4% between 1993 and 1997.4 A similartrend of increasing myopia prevalence has beenobserved in schoolchildren.1 15

The underlying explanation for high myopiaprevalence and severity in Singapore is not wellunderstood. Available data suggest that thisphenomenon is not unique to Singapore. Ahigh prevalence of myopia has also beendescribed in other east Asian urban popula-tions in Taiwan, Hong Kong, and Japan.1620 InTaiwan, a substantial increase in the prevalenceof myopia in schoolchildren has similarly beenobserved over the past few decades,16 17 al-though in Japan, the rates may have tapered

somewhat.

8 19 20

Furthermore, socio-demographic risk factors for myopia in thesepopulations appear to be similar to thosereported in the West, and include highereducation, higher income, and occupationsassociated with near work activities.68 It istherefore likely that complex and multiple fac-tors, both genetic and environmental, areinvolved.

In this paper, we systematically examine theimpact of myopia in Singapore, propose amodel to explain its high prevalence in thepopulation, and outline a strategy for myopiacontrol.

Defining the impact of myopia inSingapore

THE MEDICAL PERSPECTIVE

There is concern that blindness from myopiawill become a substantial public health prob-lem in the near future. With an ageing popula-tion (more than one third of Singaporeans willbe older than 50 years by 202521), and a risingtrend of myopia prevalence and severity,4 13 14 ithas been projected that more than 80% of theentire adult population could be myopic within

two to three decades, with a significantproportion having high myopia. Although lowand moderate myopia appears to be morebenign, high myopia may be associated with

posterior vitreous detachment,22 myopic macu-lar degeneration,2325 peripheral retinal breaks,degeneration and retinal detachment,26 andpossibly glaucoma27 and reduced contrast sen-sitivity.28 29

Nevertheless, the potential impact of myo-pia on blindness rates in the population is notclear. Data from blindness registry paint agloomy picture, but are subjected to manysources of bias (for example, low participationrate, inaccuracies in diagnosis). For example,

in Germany, which has relatively low myopiaprevalence, 1217% of blindness is reportedlyattributed to high myopia.30 In Denmark, 5%of registered blindness is related to myopia.31

Similarly, in Singapore, blindness registry dataindicate that myopia is the fourth leadingcause of blindness.32 However, populationbased prevalence survey data in the UnitedStates suggest that myopia is not a leadingcause of either visual impairment33 or blind-ness34 in adults, although the rates of myopiaare lower in the US population.10 Thus, thefull medical implications of a high myopiaprevalence in Singapore are not known at thistime.

THE PUBLIC PERSPECTIVE

Historically, the Singapore public did not

perceive myopia as a serious problem.There were no associated social stigmata,while the wearing of spectacles may even beregarded as a norm in most Singapore schools.Ocular complications aVected only a smallproportion of individuals with severe myopia,with the majority experiencing little or novision related problems. However, this attitudemay be changing. Parents have been morevocal in expressing concern about the earlyonset of myopia in children,35 while many areseeking a quick fix to myopia prevention.36 37

Greater media attention on myopia has

Br J Ophthalmol2001;85:521526 521

Defence MedicalResearch Institute,Singapore

B SeetL K H Lee

Medical ClassificationCentre, Singapore

Armed Forces,SingaporeB Seet

Singapore NationalEye Center andSingapore EyeResearch Institute,

SingaporeT Y WongD T H TanV BalakrishnanA S M Lim

Department ofOphthalmology,National University of

Singapore, SingaporeT Y WongD T H TanV BalakrishnanA S M Lim

Department ofCommunity,

Occupational andFamily Medicine,National University ofSingapore, SingaporeS M Saw

Headquarters of theSingapore Armed

Forces Medical Corps,SingaporeL K H Lee

Correspondence to:Tien Yin Wong, FRCS(Ed),MPH, Department ofOphthalmology, NationalUniversity of Singapore, 10Kent Ridge Crescent,Singapore [email protected]

Accepted for publication4 January 2001

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increased political awareness, which has led tosustained research funding for myopia inSingapore.

THE EDUCATION PERSPECTIVE

The high myopia prevalence among Singaporeschoolchildren is a particular problem.1 38 Theconsistently strong evidence of an associationbetween myopia and education712 has raisedconcerns that the rapid rise in myopia preva-

lence may be related to higher educationalattainment among Singaporeans.2 6 3 9 How-ever, whether myopia is related to education orto other socioeconomic factors (for example,urbanisation) is still unclear. For example, in astudy of comparable schoolchildren aged 78years, the myopia rate in Singapore Chinese(many originating from south China) washigher than in the city of Xiamen in southChina.40

THE MILITARY PERSPECTIVE

National military service is required for all Sin-gapore men. From the military perspective,myopia is important for various reasons.

Firstly, correction with spectacles or contactlenses may be incompatible with the stringentoccupational demands of many military voca-tions.41 Spectacles cause interface problemswith binoculars, night vision devices, protectivemasks, and other head mounted instruments.Determining a refractive error cut oV forpersonnel selection has therefore been prob-lematic, with conflicting requirements of meet-ing recruitment levels and maintaining highvisual standards as a selection criterion.42 Atthe Republic of Singapore Air Force, almost20% of military pilot applicants are rejectedbased solely on refractive status.43 Secondly,spectacle replacement presents a logistic prob-lem in military field operations. For example,

there is need for updated and customisedrefraction records of all myopic soldiers, andconstant availability of optometry services.41

Finally, there is a perception that myopiaaVects performance in visually demandingtasks like military aviation and marksmanship,although this remains unproved. Decreasedcontrast sensitivity at high spatial frequencieshas been reported with increasing myopiaseverity,28 29 and lower contrast sensitivity isassociated with impaired perception of realworld targets,44 poorer flight performance inaircraft simulators,45 and deficits in visual-spatial attention.46 Few data on the directassociation between myopia and military per-

formance exist. Available studies have notfound an association between myopia andshooting performance or military aviation.47 48

A similar project in the Singapore militaryfailed to detect significant diVerences inmarksmanship scores between myopic andemmetropic soldiers (B Seet, unpublisheddata, 1999).

THE ECONOMIC PERSPECTIVE

In Singapore, direct costs related to the correc-tion of myopia, including refractive eyewearand surgery, is expected to increase. In 1998,there were 816 optical outlets in Singapore, or

one outlet for every 3800 people.21 It has beenestimated that myopic Singaporeans spend$US90 million annually on spectacles alone.21

Refractive surgery has become increasinglypopular in Singapore, with the number of exci-mer laser machines increasing from one in1992 to eight in 2000. Refractive surgery isnow the second most common procedure aftercataract surgery, performed at a cost of about$3 million annually.49

There are also indirect costs related totreatment of myopia related complications,estimated at $22.5 million annually. About300 retinal detachments are operated on eachyear (although not all are attributable to myo-pia),50 and about 800 contact lens complica-tions, including 80 cases of severe cornealulcers, are treated at public hospitals (DTHTan, unpublished data, 2000). In fact, contactlens wear is the main risk factor for cornealulcers in Singapore.51 Additional indirectcosts are incurred by ongoing myopia researchin Singapore, estimated to be $23 millionannually.52 Thus, there is a strong economicincentive to find an eVective solution to

myopia in Singapore.

Determinants of high myopia prevalencein SingaporeDespite extensive research, the aetiologyremains unknown. It is discussed in detailelsewhere.8 5355 In this paper, we oVer a threetier model of potential determinants of thehigh myopia prevalence in Singapore (Fig 1),based on a public health approach. Thismodel forms the basis for several myopiaintervention strategies described in the nextsection.

PROXIMAL FACTORS: GENETICS AND MOLECULAR

BIOLOGY OF MYOPIA

Myopia has been postulated to arise from anunderlying genetic predisposition that makesthe eye more susceptible to environmentalmodification of its growth.56 57 The relativecontribution of genes (nature) versus environ-ment (nurture) has been the subject of intensedebate, and is probably complex.5456 Forexample, the high prevalence of myopia inSingapore and east Asia, compared with simi-larly aged white and black populations in othercountries, may be related to ethnic variationsin either genetic or environmental exposures.58

However, several lines of evidence point to astrong genetic role. Variation in genetic

exposure has been suggested as explainingdiVerences in education adjusted myopiaprevalence between young adult Chinese,Indians, and Malays in Singapore.6 14 InSingapore military conscripts, there is a strongassociation of myopia and parental history ofmyopia (odds ratio of 3.6 for myopia, 5.2 forhigh myopia), as well as sibling history ofmyopia (odds ratio of 8.6 for myopia, 14.4for high myopia).4 In other east Asianpopulations, data from twin studies showsignificantly greater intrapair variance inrefractive error among dizygotic comparedwith monozygotic twins.59 60 Data from the

522 Seet, Wong, Tan, et al

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Orinda LongitudinalStudy of Myopia

suggested that parental history of myopia

explained significantly more variance in the

childrens refractive error and ocular biomet-ric components than near work activity.61 At

the molecular level, genetic loci for certain

pathological variants of myopia have been

localised.62 63

Preliminary studies in Singaporeare currently conducted to identify candidategenes for myopia.64

Nevertheless, the pathogenic pathways formyopia outcome are not clear. Some experi-mental studies suggest that myopia developsfrom failure of either the input or output com-ponents of the active visual feedback mecha-nisms that regulate eye growth.55 For example,degrading the retinal images of animal models(input failure) has been shown to accelerateeye growth and myopia.65 Several chemicalmodulators have also been suggested as having

important molecular roles in the causation ofmyopia.66 67

INTERMEDIATE FACTORS: ENVIRONMENT RISKFACTORS FOR MYOPIA

In support of the environmental contribu-tion of myopia, studies have shown earlier ageof myopia onset in similar populations overtime17 20; higher myopia prevalence in youngercompared with older cohorts18 68; and weaker

sibling association with myopia with increasingsibling age diVerence.68 In east Asia, increasingprevalence of myopia has been attributed tochanging environmental conditions over thepast three generations.69 Some of these factorsin Singapore include having higher educa-tion,2 6 7 3 9 near work related occupations,7 70

and greater family income.7 However, the exactrelation between near work activity and devel-opment or progression of myopia remains to beestablished,71 partly because quantification ofnear work is problematic.55 72 73 74

DISTAL FACTORS: SOCIETAL INFLUENCE ONMYOPIA

Largely ignored, distal factors may also beimportant in determining the rate of myopia ina given population. Singapore is an urban citystate with a population of 3.8 million and apopulation density of almost 15 000 per squaremile.21 Ninety per cent of the population live inhigh rise apartments less than 1300 square feetin area, with a household average of 2.5 peopleper room.21 The people lead primarily indoorlifestyles, owing to the relative lack of largeopen public spaces. However, although similartrends in myopia rates are seen in Taiwan, alarge proportion of their population does notlive in such conditions. Thus, whether themacroenvironment plays an important part ininfluencing the visual cues in developing eyes

remains unclear.54In addition, Singapore has also been de-

scribed as a highly competitive society, withgreat emphasis placed on educational achieve-ments in determining career choices andadvancement. This is evident in public policiesthat have focused on developing the humanresource to serve a knowledge basedeconomy.75 76 Societal trends over the past threedecades include the early streaming ofschoolchildren within the education system;the increasing proportion of Singaporeans,particularly females, attaining higher educa-tion; and the increasing participation offemales in wage earning employment.21 Similar

social changes are seen in other countries likeTaiwan, Hong Kong, and Japan. It is also pos-sible that some of these factors are importantin explaining the high myopia prevalence ineast Asia.

Approach to myopia control in SingaporeSince the increasing prevalence of myopia wasnoted in the late 1980s, various agencies,including the ministry of health, school healthservices, and ministry of defence, have raisedconcerns about the condition.1 4 13 38 However,early eVorts to control myopia were largelyinstitution based, lacking the mandate and

Figure 1 Possible determinants of high myopia prevalence and severity in Singapore.

Distal factors

Urbanisation

Extensively built up with limited outdoor space

Confined living environment and "visual space"

Meritocracy

21 40

1 21 75 76

National policy promoting human resource development

Knowledge based economy

High emphasis on education

Intermediate factors

Indoor environment

Classroom, workplace or home environment

Inadequate or inappropriate room illumination

Near work activity

70 72 75

2 6 7 8 39 71 74

Prolonged period of formal education

Extended duration and higher intensity of near work (eg, reading)

Inappropriate refractive correction

Poor reading and writing posture or habits

Inadequate "relaxation" of the eye

Lack of outdoor activities

Excessive television and computer activity

Proximal factors

Genetics

Genetic predisposition for myopia susceptibility and severity

Biology

14 54 55 57 62 63

53 55 65 66 67

Abnormal accommodative state of the eye

Abnormal regulation of ocular growth

Abnormal scleral tissue (eg, fibroblasts)

Myopia in Singapore 523

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resources to manage the problem at thenational level. This led to the formation of amultiagency National Committee on Myopiain the late 1990s, with objectives to formulatestrategies to prevent and control myopia, aswell as to centrally plan myopia research inSingapore. Such a committee ensures focus,integration, and sustainability of local eVorts tomanage the myopia problem. Increased publicconcern has also been critical in determining

political interest and funding for myopiaresearch.

THE VISION CARE PROGRAMME

There are presently a number of options formyopia prevention and control.8 77 Many ofthese are directed atproximalfactors, includingtopical eyedrops like atropine,78 opticallenses,79 80 rigid contact lenses,81 intraocularpressure lowering agents,82 biofeedback meth-ods,83 and traditional techniques like Chineseeye relaxation exercises.84 However, theeVectiveness of some of these methods isquestionable, and there is inadequate scientificevidence for implementation in a population

setting. Many clinical trials lacked randomisa-tion, had high dropout rates, or failed toaccount for confounding.8 On the other hand,it is diYcult to prescribe interventions toreduce exposure to either intermediate or distalfactors like education, near work, and livingconditions.

In the absence of definitive interventions, abroad vision care programme was initiated inSingapore schools.85 This is largely based onexisting evidence that prolonged near work(and possibly poor visual environment) maycontribute to myopia onset and progression,and on the hypothesis that relieving eye strainand promoting visual health will have benefi-cial eVects. This programme comprises annual

vision screening in schoolchildren, appropriaterefractive correction, eye relaxation tech-niques, promotion of outdoor activities, andguidelines on classroom materials and illumi-nation. An emphasis is placed on educatingschoolchildren, parents, and teachers on gen-eral eye care, good reading habits, and myopia.The next phase of the programme is tocombine these with clinical trials involvingpharmacological and optical interventions,7881

or even controversial techniques like eyerelaxation exercises.84 This programme isintended to evolve as our knowledge of myopiaincreases.

PUBLIC EDUCATION AND CLINICAL PRACTICE

GUIDELINES

The inconsistent results of current myopiatreatment have generated confusion in an anx-ious population. The ministry of health hasmade eVorts to conduct regular public forums,health fairs, and community based eye screen-ing programmes in Singapore. To preventexcessive use and abuse of putative myopiatreatment modalities, clinical practice guide-lines are also issued to establish clear indica-tions and limitations of contact lens86 and laserrefractive surgery,87 in the management ofmyopia.

MYOPIA RESEARCH IN SINGAPORE

The goal of myopia research in Singapore liesin developing practical approaches that willultimately modify the biological course of thecondition, ideally to prevent the onset of myo-pia altogether. In line with this, basic scienceresearch is directed towards identifying geneticmarkers of myopia,64 understanding cellularpathways of emmetropisation,88 and develop-ing animal models for clinical trials. Clinical

research is centred on randomised trials to pre-vent or slow myopia progression (topical eyedrops, rigid contact lenses),81 and to correctmyopia (refractive surgery trials).87 Epidemio-logical studies evaluate putative risk factors ofmyopia in schoolchildren1 15 71 military person-nel,4 6 and adults.7 89 Finally, additional re-search in the military evaluates visual perform-ance in myopes,29 30 developing functionalvisual criteria for personnel selection,4 andoptimising visual function for myopes underdiVerent operational settings.90

ConclusionThe prevalence of myopia in Singapore is one

of the highest worldwide. Current data indicatethat both the rate and severity of myopia maybe increasing over time. A similar epidemicappears to be occurring in other east Asianpopulations, and it is possible that ocular mor-bidity related to myopia may constitute animportant clinical, public health, and eco-nomic problem over the next two to three dec-ades. Because knowledge about myopia isincomplete and potential therapeutic measureshave yet to be proved consistently eVective, apragmatic public health approach has beenadopted in Singapore, comprising a visioncare programme in schools, regular publiceducation, and an integrated myopia researchstrategy.

DedicationThe authors dedicate this paper in memory of the late Sek JinChew, FRCS, PhD, (195998), who had been one of the driv-ing forces behind myopia research in Singapore and inter-nationally.

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1st Asia Pacific Forum on Quality Improvement in Health Care

Three day conference

Wednesday 19 to Friday 21 September 2001

Sydney, Australia

We are delighted to announce this forthcoming conference in Sydney. Authors are invited tosubmit papers (call for papers closes on Friday 6 April), and delegate enquiries are welcome.

The themes of the Forum are:

x Improving patient safetyx Leadership for improvementx Consumers driving changex Building capacity for change: measurement, education and human resourcesx The context: incentives and barriers for changex Improving health systemsx The evidence and scientific basis for quality improvement.

Presented to you by the BMJ Publishing Group (London, UK) and Institute for HealthcareImprovement (Boston, USA), with the support of the the Commonwealth Department ofHealth and Aged Care (Australia), Safety and Quality Council (Australia), NSW Health(Australia), and Ministry of Health (New Zealand).

For more information contact: [email protected] or fax +44 (0)20 7383 6869


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