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Visual fieldsAssessment of the visual field in
patients with AD or PD should involve
a technique that assesses magno-
cellular function.1 The usefulness of
frequency doubling technology (FDT)
as employed by the Zeiss FDT screener
has previously been described,2,3 whilst
other techniques include the Bjerrum
(tangent) screen and campimeter,
which assess the initial perception of
a moving target to which the magno-
cellular system is most sensitive. Such
methods may reveal a constricted field
and accompanying enlarged blind spot.4
Optometric Management of Alzhiemer's and Parkinson's Diseases
However, practitioners should beware
that it can be difficult to accurately assess
visual fields in patients with AD or PD
using automated threshold methods,
due to poor fixation/attention. As such,
some alternative and inexpensive
methods can be adopted instead.
Temporal hand confrontationFace the patient and ask them to look at
your nose binocularly (the nose acts as
a septum so there is no need to occlude
one eye). Hold your hand close to the
side of your face and ask the patient if
they can see it. If they can, slowly move
your hand away to the side, asking
the patient to notify you if the hand
disappears. When it does disappear,
move the hand out further and then
bring it in slowly until the patient tells
you they can see it again. Repeat for both
eyes and compare to the expected range.
Repeating the test with fingers spread
apart, and asking the patient to tell you
when they are aware of the separated
fingers, helps to assess the ability to
process detail within the peripheral
field; this field can be quite small.5
Laser pointer on wallThe patient sits one metre from a plain
wall and is asked to fixate a mark directly
in front of them (eg, a pin or a cross on
a post-it note). Testing monocularly, the
patient fixates this as you move a laser
pointer light towards the fixation target
from various peripheral directions.6
Results are compared akin to the Bjerrum
chart or the Fincham Sutcliffe chart; these
charts are more useful as they have the
degree markings written on the screen.
In either case, the measured visual
field can be very restricted if compared
to static threshold visual fields. In
addition, comparing this field to that
found using the Fincham Sutcliffe chart
in its conventional flashing light mode
will demonstrate a significant difference.
Indeed, though they may have identified
the correct number of lights, their
awareness of stimulus location is poor
(difference between static and motion
processing). This demonstrates one of the
causes of mobility problems that people
with PD and AD can have along with
difficulties with reading and posture
(downward head tilts are common).7
Awareness of PractitionerThis is a very simple test of peripheral
awareness that requires no specialist
equipment or training and can be
used by a doctor or nurse in a person’s
AgEINg VIsION PART 4 COuRsE CODE: C-15687 O/D
geoff shayler Bsc, FCOptom, FCsOPatients with Alzheimer’s disease (AD) and Parkinson’s disease (PD)
experience neurological damage to magno-, parvo- and konio-cellular
visual processing streams, although the magno-cellular system appears to
be affected most. Previous articles in this series have discussed a simplistic
model of visual processing and presented the pertinent visual features
of AD and PD. The current article discusses how such patients could be
examined in optometric practice with respect to this model and visual
features, to better identify and manage difficulties that patients experience.
Figure 1 Visual field assessment by “awareness of practitioner”
Practitioner
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home. Stand three metres in front of
the patient and ask them to fixate your
nose. The patient is asked to report
how much of the practitioner’s body
they are aware of. As the practitioner
is looking at their patient, they can
monitor fixation and compare the
patient’s field to their own (Figure 1).
ReadingOptometrists will commonly assess a
near reading addition power but often
overlook the available range of clear
vision (accommodative flexibility; af),
which can actually be reduced due
to the visual field and affects on the
magno-cellular (kinetic or awareness)
pathway.4,8,9 This was confirmed by a
retrospective study during a six-month
period, revealing a direct relationship
between the near range of vision and the
visual field assessed using the awareness
of practitioner technique; patients wore
a +2.25DS near add and had normal
near visual acuity (VA) (Figure 2). From
this relationship, it can be seen that a
typical awareness field of a patient with
PD that reaches “down to the waist”,
corresponds to a clear range of reading
(af) of only 15cm.10 Therefore, adding
these simple tests, which take very
little time, can alert the optometrist to
potential visual processing problems
that require further investigation.
Eye tracking and ocular motilityPatients with dementia have significantly
worse smooth-pursuit tracking
movements than people with either
pseudodementia or elderly normal
controls.11,12 It is postulated that the
ocular motor changes seen in PD are
contingent upon functional dopamine
levels in the basal ganglia. Clinical
improvement with dopaminergic drugs
has shown an improvement of saccadic
accuracy and smooth pursuit gain.13
As such, it is important to assess ocular
motility, looking for head movements, loss
of fixation, jerky eye movements, postural
instability, and reduced convergence. Visual acuity and contrast sensitivityThough VA in patients with PD and AD is
initially normal, it may reduce gradually
through disease processes such as cataract
and age-related macular degeneration
(AMD), bringing with it associated effects
on the visual field eg, general reduction
in sensitivity (consider this as Traquair’s
“Island of vision” sinking into the sea,
with a higher island peak corresponding
to a better VA).14 Furthermore, there can
be a reduction in contrast sensitivity,
indicating a need to assess this using,
for example, the Vistech chart or
Bailie Lovie charts, and to monitor for
progressive changes in AD and PD.15
Visual mid-line shift syndromeSome patients with AD and PD
experience difficulty with walking
in a straight line, often associated
with head tilts/turns and postural
problems that affect the shoulders,
lower back and neck. These symptoms
can be due to a condition called visual
mid-line shift syndrome, where objects
directly in front of an individual are
perceived to be offset to the side;16
typically the shift is in the same
direction as the head tilt/turn eg, if the
patient has a head turn to the left, the
object will be perceived as being offset
to the left of centre (Figure 3). Visual
mid-line shift syndrome results from
dysfunction of the ambient magno-
cellular system, which causes a shift in
their concept of the visual mid-line.17
This condition can be elicited by a
test similar to confrontation. Have the
patient stand as for a motility test, hold
your fixation target off to the side and
move it slowly across in front of them.
The patient is required to tell you when
the target is in front of their nose. Check
the position and if it is not centred, a
visual mid-line shift can be identified.
When carrying out the test, do not stand
directly in front of the patient, as this will
give them a centring reference. Repeat
Figure 2 The relationship between the visual field as estimated by “awareness of practitioner” and the range of clear near vision (accommodative flexibility; af)
Awareness of practitioner (deg)
Ave
rage
af (
cent
imet
res)
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nerve fibres), careful investigation
of this potential condition should be
undertaken, with regular monitoring of
the optic nerve head appearance and
visual fields; the latter should include
magno-cellular assessment, as mentioned
earlier, along with static threshold
tests for monitoring progression.
Optometric careTreatment regimes for patients with AD
and PD are not aimed at treating the
medical condition but rather to reduce
stress and visual problems encountered,
in order to improve quality of life. For
example, patients with tremor may
not be able to hold a book to read
comfortably and so one can prescribe a
lower reading add, advise good lighting
and/or suggest the use of non-visual aids
eg, placing the book on a table. Many
optometric assessments will require
reliance on objective techniques such
as retinoscopy and Sheridan-Gardner
VA testing, due to the difficulty in
obtaining accurate subjective responses.
Patients with dementia are typically
less likely to have regular eye exams,
increasing the consequent risk of
sight loss from typical age-related
sight problems. Assessment of these
patients under mydriasis is therefore
essential to identify sight-threatening
disease. Where possible, treatment of
these problems can improve quality
of life by helping mobility and
posture. Improving functions such as
motion awareness, contrast, VA, and
colour vision can enable a person to
look at magazines and watch TV too.
Lens prescribingThe near range of clear vision can be
modified with the prescription of yoked
prisms, typically 2∆ base down each
eye,25 which will increase the functional
near visual field, improve the near point
of convergence and improve reading
from the other side too. Also assess the
patient’s posture, looking for head tilt,
whether the shoulders and pelvis are
level, and if the spine is curved to the
side or forward (particularly seen in PD).
Visual mid-line shift can also be
evaluated with the Van Orden star18
and the VTE Spatial Localisation
Board18 (Figure 4). The latter allows the
optometrist to quickly assess a patient's
spatial localisation in real space and time;
determine x, y and z axis spatial warps
in nine primary meridians and record
patient responses for pre- and post-test
data (especially good for documenting
visual mid-line shifts in mild traumatic
brain injury) and quantify immediate
effects of lenses and prisms.19,20,21
Colour visionPeople with AD may experience loss
of blue/violet sensitivity, which may
be associated with damage to the
koniocellular system. Such defects
are not adequately detected by the
Ishihara test and so the Farnsworth
D15 or the City University (TCU)
tests ought to be used instead (see
previous articles in Optometry Today
for details on colour vision testing).22,23
Retinal assessmentRetinal abnormalities in early AD
and PD include a specific pattern of
retinal nerve fibre layer (RNFL) loss,24
narrowing of veins, and reduced
blood flow. Loss of retinal ganglion
cells may reflect degenerative change
in the brain in these conditions.24 As
software for digital retinal cameras and
optical coherence tomography (OCT)
improves, a greater understanding of
these early changes will be obtained.
glaucoma As glaucoma can develop faster in
patients with AD or PD (causing damage
to magno-, parvo- and konio-cellular
Figure 3 Affect of visual mid-line shift on posture. Courtesy of Dr W Padula OD
Figure 4 The VTE Spatial Localization Board
Optometric phototherapy (syntonics)Syntonics or optometric
phototherapy is the branch of
ocular science dealing with the
application of selected light
frequencies through the eyes31 to
improve cortical processes such as
in cases of brain injuries, emotional
disorders,32 and seasonal affective
disorder (SAD). A number of studies
have shown expansion of visual
fields in children with learning
difficulties33-34,35 and similar changes
could be expected of people with PD36 as
a result of improved form and motion
coherence processing, through inhibition
of melatonin.37 Green light (505nm) is the
most effective for suppressing melatonin
production and is utilised in Sunnex
Biotechnologies Lo-LIGHT lamps.38 Light
therapy was reported to slow "cognitive
deterioration" by 5% and depressive
symptoms fell by 19%,36 however,
further research in this area is required.
ConclusionWithin the panoply of age-related
disease, AD and PD are serious conditions
that significantly affect a person’s quality
of life. Knowledge of the visual problems
associated with these conditions, and how
simple changes such as improving contrast
in the home or prescribing different lens
forms, might help to extend quality of life
for these patients. Eye care professionals
need to consider a variety of tools at their
disposal to do this and it is hoped that these
articles will stimulate further research.
ReferencesSee http://www.optometry.co.uk
clinical/index. Click on the article
title and then download "references"
For the module questions to this article, please turn to page 49.
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speed and comprehension.
Base down prisms will also
have the effect of “lifting the
environment”, aiding those
patients with “head down”
postural problems. Base up
prisms can also be helpful but may
increase the tendency for head
down posture.19-21 Horizontal
yoked prisms can help with
mid-line shift syndrome.26,27
Consideration should be
given to the possibility that
postural problems and visual
field deficits may impair the
effective use of varifocal spectacle
lenses and so single vision lenses ought
to be preferred, especially for mobility
and reading.28 An alternative option
is a degressive varifocal lens, such as
Rodenstock Ergo, Sola Access, or Varilux
computer 2V, especially for those people
who are using a VDU.25 Photochromic or
contrast enhancing lenses may also be
considered for patients with photophobic
or contrast problems, respectively, and
for protection from ultraviolet (UV) light.
Future techniques?A new visual field test, the Motion
Displacement Test (MDT) (Figure
5), is currently in development at
Moorfields Eye Hospital and The
Institute of Ophthalmology, UCL, in
collaboration with City University,
London. This computer-based test
works primarily on the “awareness of
movement displacement” associated
with the magno-cellular pathway.
Therefore it may prove useful to identify
and monitor these deficits. However,
present research has concentrated
on glaucoma detection only.29
Results obtained with the City
University CAD test, developed in
association with the Civil Aviation
Authority, provide an efficient means
of detecting and classifying even
minimal deficiencies in colour vision,
by evaluating red/green and blue/yellow
colour detection thresholds using an
internationally recognised colour system.
As such this can be used to monitor
changes in colour perception, disease
progression, and/or therapy outcomes.
However, the cost of this test suggests it may
only be appropriate in specialist clinics.30
Optometric vision therapyTechniques used to develop the visual
system in children with learning
difficulties and in adults with mild
traumatic brain injury could also be
applied to improving visual function
in people with AD and PD. Based on
the Skeffington concept (see part 1 of
this series, Optometry Today January
14 2011), optometrists can train specific
elements of the visual processing system:
1. Anti-gravity – to improve posture,
balance, and postural/primitive reflexes
2. Centring – to improve pursuit &
saccadic eye movements, convergence,
and accommodation
3. Identification – to improve visual
discrimination, closure, perception, and
memory
4. Speech/auditory – to improve
visualisation, sequencing, laterality, and
developing ideas/concepts
Figure 5 The Moorfields MDT field test