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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