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Some patients will attend clinical<br />

practice complaining of problems with<br />

near tasks such as reading or VDU work.<br />

This is usually due to a comitant<br />

deviation and, although troublesome<br />

because of <strong>the</strong> symptoms produced, <strong>the</strong>y<br />

are never life-threatening. However,<br />

patients may also attend with<br />

heterotropias. Whilst <strong>the</strong>se are usually<br />

long-standing deviations, patients may<br />

occasionally present complaining of<br />

sudden onset diplopia with unnoticed<br />

attendant heterotropia. The distinction<br />

between long-standing and recent onset<br />

heterotropia must be clearly made as<br />

acquired deviations usually indicate<br />

active pathology which can be lifethreatening.<br />

If not detected and<br />

adequately managed, <strong>the</strong>se may result in<br />

malpractice claims. In order to<br />

differentiate between such entities, a<br />

sound knowledge of <strong>the</strong> extraocular<br />

musculature and innervation is essential.<br />

BV FACTS<br />

Ten percent of all primary care patients<br />

exhibit a BV problem, and 2-3% of all<br />

subjects exhibit a heterotropia.<br />

Therefore, an optometrist that sees an<br />

average of 15 patients per day (75 per<br />

week), can expect approximately seven<br />

with a BV anomaly and one or two with<br />

a heterotropia.<br />

Lyndon Jones, BSc, PhD, FCOptom, DCLP, DOrth, Frank Eperjesi, BSc, MCOptom and<br />

Bruce Evans, BSc, PhD, FCOptom, DCLP<br />

Binocular vision evaluation in practice<br />

Some form of binocular vision (BV) evaluation should be undertaken on every<br />

patient. The equipment required is easily obtainable, easy to use and, relative<br />

to o<strong>the</strong>r optometric instrumentation, of low cost. General BV assessments can<br />

be conducted with a cover stick, near and distance targets, an RAF rule, prism<br />

bars, pen torch, Mallett Unit and tape measure (Figure 1).<br />

Figure 1 BV equipment<br />


Appropriate examination of <strong>the</strong> BV<br />

system requires an understanding of<br />

<strong>the</strong> anatomy of <strong>the</strong> visual apparatus,<br />

<strong>the</strong> motor system and coordinated eye<br />

movements, as well as <strong>the</strong> sensory<br />

system, which under normal<br />

circumstances integrates two<br />

monocular inputs to form a single<br />

percept.<br />


As mentioned above, BV equipment is<br />

low cost, easily available and easy to<br />

use - <strong>the</strong> difficult part is in <strong>the</strong><br />

interpretation; this is easier if <strong>the</strong><br />

techniques are carried out correctly<br />

and accurate information is obtained.<br />

Particular attention needs to be paid to<br />

working distances and <strong>the</strong> speed at<br />

which procedures such as <strong>the</strong> cover test<br />

are conducted. A common error is not<br />

to allow enough time for dissociation<br />

and not to adequately occlude <strong>the</strong> eye<br />

under <strong>the</strong> cover. Poor technique results<br />

in inaccurate data, which makes<br />

diagnosis difficult, if not impossible.<br />


General observations of <strong>the</strong> patient are<br />

important and can be made on first<br />

sight of <strong>the</strong> patient and during history<br />

and symptoms. Head turns and tilts<br />

often indicate some problem with<br />

extraocular muscles and tend towards<br />

<strong>the</strong> field of action of <strong>the</strong> underacting<br />

muscle to help <strong>the</strong> patient avoid<br />

binocular embarrassment. Postural<br />

changes and excessive effort during<br />

visual tasks may indicate that all is not<br />

well. Patients will often experience<br />

more difficulty during <strong>the</strong> test, as <strong>the</strong>y<br />

become tired. This is especially <strong>the</strong> case<br />

if <strong>the</strong>y are only just coping and <strong>the</strong>n are<br />

forced to operate beyond <strong>the</strong>ir comfort<br />

zone.<br />



Since amblyopia and heterotropia present<br />

at specific ages, it is important to elicit<br />

details of onset and <strong>the</strong> course of <strong>the</strong><br />

condition. This is useful in determining<br />

<strong>the</strong> likely prognosis and if referral is<br />

necessary. Take note of <strong>the</strong> presenting<br />

problems or concerns, especially double<br />

vision and if this is present at distance or<br />

near, or when looking in a particular<br />

direction. Is it worse at a certain time of<br />

<strong>the</strong> day? Is <strong>the</strong>re any history of lazy eye, eye<br />

turns and, if so, what was <strong>the</strong> age at onset?<br />

Ask about history of spectacle wear and<br />

from what age. Also ask about previous<br />

HES visits, previous trauma, patching or<br />

orthoptic exercises, and any prisms in<br />

glasses. Birth history, pre-term deliveries,<br />

forceps or Caesarian delivery and <strong>the</strong><br />

health of <strong>the</strong> baby after parturition are also<br />

important areas to look at.<br />


Ask about any family history of<br />

heterotropia, amblyopia or spectacle<br />

wear. There is a 10x increased risk if a<br />

parent has a heterotropia (incidence of<br />

anomaly 25% vs. 2.5%); 86% incidence<br />

of heterotropia if family history of<br />

heterotropia and child is >+2.00DS.<br />


Ask about general health, current<br />

medication and previous surgery. Is <strong>the</strong>re<br />

any hypertension, diabetes, heart disease<br />

or thyroid dysfunction?<br />


Ask about family history of hypertension,<br />

heart disease, thyroid problems and<br />

diabetes.<br />


Be aware of visual acuity at various ages,<br />

and use appropriate tests for <strong>the</strong> age of<br />

<strong>the</strong> patient. Also be aware of <strong>the</strong><br />

crowding phenomenon and its effects on<br />

acuity measured with single and linear<br />

optotypes. Problems often arise for<br />

sustained near vision with IVN palsy<br />

continued overleaf<br />


Binocular vision evaluation in practice<br />

although distance vision is normal, so<br />

always carry out motility on those who<br />

complain of near vision problems (see<br />

later). With very young patients<br />

alternate occlusion can be used along<br />

with preferential looking, e.g. Keeler or<br />

Cardiff Acuity Cards. For older children,<br />

you can try matching pictures or shapes,<br />

e.g. Kay, Ffookes symbols, and for school<br />

age children Sheridan Gardiner,<br />

Sonksen-Silver or Glasgow Acuity Cards.<br />


This is a very important test as it can<br />

easily differentiate between a<br />

heterotropia and a heterophoria. It can<br />

also be used to estimate or measure <strong>the</strong><br />

direction and size of <strong>the</strong> deviation, and<br />

to give some indication whe<strong>the</strong>r it is<br />

compensated or not.<br />

Choose a suitable target in order to<br />

induce accommodation, do so slowly<br />

with good lighting. Cover, uncover,<br />

remove cover vertically and ensure <strong>the</strong><br />

eye is covered to avoid peripheral fusion<br />

locks. If amblyopia is suspected, take a<br />

little longer before removing <strong>the</strong> cover as<br />

<strong>the</strong> amblyopic eye requires longer to take<br />

up fixation. Decide if movements<br />

indicate a heterotropia, heterophoria or<br />

orthophoria, eso or exo, hypo or hyper.<br />

Estimate <strong>the</strong> size and speed of recovery<br />

and measure with a prism bar if you wish.<br />

Then do alternate cover and look for an<br />

increase size of deviation which is useful<br />

for small vertical deviations. Watch <strong>the</strong><br />

upper lids as any movement may indicate<br />

a vertical problem. Do not assume <strong>the</strong>re<br />

is no heterotropia if you see no<br />

movement; <strong>the</strong>re may be a microtropia<br />

with abnormal retinal correspondence so<br />

consider a four base-out prism test to<br />

determine if suppression is present.<br />

Figure 2 NPC assessment<br />



This is only applicable for binocular<br />

patients and is particularly important for<br />

symptomatic exophores. It is important<br />

to choose an appropriate target, ei<strong>the</strong>r<br />

<strong>the</strong> dot and line on <strong>the</strong> RAF rule, or a<br />

near 6/9 letter, which is considered to be<br />

<strong>the</strong> clinical standard. It is absolutely<br />

inappropriate to use a pen-top. NPC is<br />

most accurately measured with <strong>the</strong> RAF<br />

rule, in <strong>the</strong> depressed position - 45<br />

degrees, and a slow speed (Figure 2).<br />

In order to check for fatigue it should<br />

be measured three times near <strong>the</strong><br />

beginning of <strong>the</strong> assessment and twice at<br />

<strong>the</strong> end. The value can be noted in terms<br />

of break (ei<strong>the</strong>r when <strong>the</strong> subject reports<br />

diplopia [subjective result] or when <strong>the</strong><br />

observer notices one or both eyes diverge<br />

[objective result]) and in terms of<br />

recovery (ei<strong>the</strong>r when <strong>the</strong> subject<br />

reports single vision or <strong>the</strong> observer<br />

notices that both eyes are pointing to <strong>the</strong><br />

test target). Both break and recovery are<br />

measured to <strong>the</strong> nearest half centimetre.<br />

A remote NPC with a break greater<br />

than 10cm is considered to be <strong>the</strong> most<br />

consistent finding in subjects with<br />

convergence insufficiency. Fatigue needs<br />

to be assessed as a subject may be able to<br />

produce one good result with <strong>the</strong> RAF<br />

rule, but <strong>the</strong> NPC may increase with<br />

fur<strong>the</strong>r testing. Many subjects report <strong>the</strong><br />

occurrence of symptoms only after<br />

several minutes of near point task<br />

performance.<br />


These (also called horizontal vergence<br />

reserves and prism vergences) can be<br />

measured in several ways. Orthoptists<br />

tend to use a prism bar (step vergence).<br />

Figure 3 Fusional reserves assessment<br />

Those optometrists with an interest in<br />

this field tend to use a Risley rotating<br />

prism (smooth vergence) ei<strong>the</strong>r<br />

monocularly in a trial frame, or<br />

binocularly in a phoropter. The results<br />

differ according to which procedure is<br />

used so, when making records, it is<br />

important to note <strong>the</strong> instrument used<br />

(Figure 3).<br />

Base-in and base-out values for near<br />

are usually <strong>the</strong> most useful although<br />

distance values can also be obtained.<br />

The blur, break and recovery points for<br />

both base directions need to be noted.<br />

This is a direct measure of <strong>the</strong> fusional<br />

vergence available to compensate for a<br />

phoria. The blur point is reached when<br />

<strong>the</strong> subject has used all <strong>the</strong>ir fusional<br />

reserves and has to use accommodative<br />

convergence to keep <strong>the</strong> test target<br />

single. As accommodative convergence<br />

is brought into play, <strong>the</strong> subject<br />

accommodates and <strong>the</strong> test target<br />

becomes blurred. The break point<br />

corresponds to <strong>the</strong> point when <strong>the</strong><br />

subject no longer has any fusional or<br />

accommodative vergence remaining and<br />

<strong>the</strong> test target becomes double.<br />

Norms are age-dependent. It is<br />

possible to have normal convergence<br />

amplitude as measured with <strong>the</strong> RAF<br />

rule push-up test and still have a<br />

vergence problem. This is known as<br />

fusional vergence dysfunction.<br />


This is a measure of <strong>the</strong> maximum<br />

amount of accommodation an individual<br />

can exert and is usually measured using<br />

<strong>the</strong> RAF rule with <strong>the</strong> smallest text<br />

readable. It should be conducted<br />

monocularly and binocularly and<br />

repeated at least three times for each<br />

situation in order to assess for fatigue.<br />

This is important in esophores and<br />

symptomatic patients with NV problems.<br />

Ask <strong>the</strong> patient to read out loud <strong>the</strong><br />

smallest line <strong>the</strong>y can see, <strong>the</strong>n move <strong>the</strong><br />

target in and watch for saccades to make<br />

sure <strong>the</strong>y are accommodating on <strong>the</strong><br />

target; measure monocularly and<br />

binocularly and repeat to check for<br />

fatigue.<br />


This determines <strong>the</strong> speed of<br />

accommodative change. The dioptric<br />

accommodative stimulus is alternated<br />

between two different levels and <strong>the</strong><br />

subject reports when a letter target is<br />

seen clearly after each alternation in<br />

34<br />


Binocular vision evaluation in practice<br />

Figure 4 Accommodative facility assessment<br />

accommodative stimulus. The examiner<br />

counts <strong>the</strong> number of cycles completed<br />

in one minute (one cycle being <strong>the</strong><br />

change from one stimulus level to <strong>the</strong><br />

o<strong>the</strong>r and back again). Accommodative<br />

stimulus can be varied ei<strong>the</strong>r by lens<br />

power changes or by viewing distance<br />

changes. The first is referred to as lens<br />

rock and <strong>the</strong> second as distance rock,<br />

indicating that <strong>the</strong> accommodative<br />

stimulus is ‘rocked’ back and forth.<br />

The standard method of testing<br />

accommodative facility is a lens rock<br />

procedure using a pair of +2.00D lenses<br />

on one side of a flipper bar, and -2.00D<br />

lenses on <strong>the</strong> o<strong>the</strong>r side, although also<br />

available as ±1.00D and ±3.00D. The<br />

test is begun with <strong>the</strong> +2.00D lenses<br />

over <strong>the</strong> subject’s refractive correction.<br />

A test distance of 40cm is usually used<br />

with <strong>the</strong> reduced Snellen letters at a 6/6<br />

to 6/12 acuity demand for monocular<br />

testing (Figure 4). This type of target<br />

has no suppression control and it is more<br />

appropriate to use ei<strong>the</strong>r <strong>the</strong> Bernell<br />

vectogram SOV9 or <strong>the</strong> vertical fixation<br />

disparity bars on <strong>the</strong> near Mallett unit<br />

for binocular testing. Both need to be<br />

used with polarising filters.<br />

Some clinicians suggest that it may<br />

be more appropriate to train <strong>the</strong><br />

monocular accommodative facility prior<br />

to <strong>the</strong> binocular facility, especially if <strong>the</strong><br />

binocular lens rock performance is<br />

limited by fusional vergence dysfunction.<br />

Cut-offs for test failure using<br />

+2.00D/-2.00D flippers and a 40cm<br />

viewing distance for children and adults<br />

up to 30 years of age, are less than 11<br />

cycles per minute for monocular testing<br />

and less than 8 cycles per minute for<br />

binocular testing. Norms are agedependent.<br />

During binocular lens rock<br />

testing, adjustments in fusional vergence<br />

must occur to compensate for <strong>the</strong><br />

changes in accommodative vergence.<br />

Therefore, subjects may pass <strong>the</strong><br />

monocular lens rock but fail <strong>the</strong><br />

binocular lens rock facility if a vergence<br />

disorder is present.<br />


During accommodation for near-point<br />

viewing, <strong>the</strong> retina usually is conjugate<br />

with a point slightly behind <strong>the</strong> object of<br />

regard. For near-point targets,<br />

accommodative response is usually<br />

slightly less than <strong>the</strong> accommodative<br />

stimulus. The amount by which <strong>the</strong><br />

dioptric accommodative response is less<br />

than <strong>the</strong> dioptric accommodative<br />

stimulus is <strong>the</strong> lag of accommodation.<br />

This category of accommodation tests<br />

can be fur<strong>the</strong>r divided into: tests that<br />

measure <strong>the</strong> lag of accommodation; and<br />

tests in which lens power is changed to<br />

alter accommodative stimulus to <strong>the</strong><br />

point at which dioptric accommodative<br />

stimulus and dioptric accommodative<br />

response are equal.<br />

Monocular estimate method (MEM)<br />

dynamic retinoscopy is <strong>the</strong> procedure<br />

currently preferred by <strong>the</strong> authors. A test<br />

card with an aperture in <strong>the</strong> centre is<br />

used for dynamic retinoscopy so that <strong>the</strong><br />

examiner can observe <strong>the</strong> retinoscopic<br />

reflex close to <strong>the</strong> subject’s visual axis<br />

through <strong>the</strong> aperture. In MEM dynamic<br />

retinoscopy, <strong>the</strong> amount of <strong>the</strong> lag of<br />

accommodation is estimated by judging<br />

<strong>the</strong> width, speed and brightness of <strong>the</strong><br />

retinoscopic reflex. The test card and <strong>the</strong><br />

retinoscope are placed at <strong>the</strong> same<br />

distance from <strong>the</strong> subject’s spectacle<br />

plane, usually 40cm (Figure 5).<br />

With <strong>the</strong> retinoscope in <strong>the</strong> plane<br />

mirror mode, ‘with motion’ indicates a<br />

Figure 5 Accommodative lag assessment<br />

lag of accommodation and ‘against<br />

motion’ indicates a lead of<br />

accommodation. Neutrality indicates<br />

that <strong>the</strong> accommodative stimulus and<br />

accommodative response are equal. The<br />

examiner’s estimate of <strong>the</strong> amount of<br />

plus power that would be required to<br />

neutralise <strong>the</strong> ‘with motion’ is <strong>the</strong><br />

estimate of <strong>the</strong> lag of accommodation.<br />

The estimate of <strong>the</strong> lag can be confirmed<br />

by very briefly placing a plus lens equal in<br />

power to <strong>the</strong> estimated lag over one eye<br />

and quickly checking to see whe<strong>the</strong>r<br />

neutrality is observed. The lens should<br />

only be in place a half-second or less so<br />

that a change in accommodative<br />

response is not induced. School age<br />

children are reported to have a mean lag<br />

of +0.34D. Most non-presbyopic<br />

subjects have lags of 0 to +0.75D with<br />

MEM retinoscopy.<br />


To examine <strong>the</strong> action of a muscle and<br />

that of its yoke muscle, a motility test can<br />

be performed. In this test a pen-torch is<br />

moved in front of <strong>the</strong> subject in a star<br />

pattern, whilst <strong>the</strong> subject keeps <strong>the</strong>ir<br />

head and neck still. By moving <strong>the</strong> eyes<br />

in this manner, <strong>the</strong> maximal actions of all<br />

<strong>the</strong> extraocular muscles can be checked;<br />

<strong>the</strong> corneal reflexes should be observed.<br />

For example, <strong>the</strong> action of <strong>the</strong><br />

superior rectus (SR) muscle is best<br />

evaluated by placing <strong>the</strong> eye in an<br />

abducted position and checking <strong>the</strong><br />

degree of elevation, which can be<br />

achieved. Poor function of this muscle<br />

will be indicated by a reduced ability to<br />

elevate <strong>the</strong> eye in this abducted position<br />

and diplopia in <strong>the</strong> field of action of <strong>the</strong><br />

weakened muscle. The patient should be<br />

asked - “Is <strong>the</strong> double vision horizontal,<br />

vertical or oblique?” A cover test<br />

conducted in ‘up’ and ‘right’ gaze (in a<br />

case of a right SR weakness) will also<br />

show a hypotropia which is maximal in<br />

this position when compared with all<br />

o<strong>the</strong>r peripheral positions.<br />

Patients may present with ei<strong>the</strong>r a<br />

partial loss (paresis) or complete loss<br />

(paralysis) of muscle function. These<br />

terms are often used synonymously.<br />

Maximum and minimum fields of<br />

diplopia can be detected and an attempt<br />

made to try and isolate muscle or at least<br />

a pair of muscles. Alternatively, <strong>the</strong> eye<br />

with <strong>the</strong> outer most image has <strong>the</strong><br />

underacting muscle; images can be<br />

continued overleaf<br />


Binocular vision evaluation in practice<br />

enhanced by using red and green goggles.<br />

It is important to determine whe<strong>the</strong>r <strong>the</strong><br />

underaction is recent or long-standing<br />

and if <strong>the</strong> diplopia is sudden or of gradual<br />

onset. It should be noted that <strong>the</strong> vertical<br />

meridian is not a diagnostic direction of<br />

gaze, however, it is still useful to test in<br />

this direction, since it will help to identify<br />

A and V patterns more easily.<br />



Fixation disparity is a technique familiar<br />

to most optometrists and will not be<br />

discussed in detail. The patient should be<br />

instructed to compare <strong>the</strong> position of <strong>the</strong><br />

green markers with and without <strong>the</strong><br />

Polaroid. Allow <strong>the</strong> patient to settle with<br />

<strong>the</strong> Polaroid and check that <strong>the</strong>y can see<br />

both markers, i.e. <strong>the</strong>y are not<br />

suppressing. Allow <strong>the</strong> patient to adapt<br />

by reading a line of text and <strong>the</strong>n<br />

neutralise any displacement with <strong>the</strong><br />

minimum prism - this is termed <strong>the</strong><br />

aligning prism, or small spheres. The<br />

displacement of <strong>the</strong> marker is referred to<br />

as fixation disparity. The markers may<br />

move back and forth across <strong>the</strong> neutral<br />

position indicating binocular instability;<br />

if <strong>the</strong> markers flicker this may be due to<br />

alternate suppression or retinal rivalry.<br />


Suppression is a negative adaptation to<br />

diplopia; it can vary in its intensity on a<br />

continuous scale from shallow to deep as<br />

well as in its size and position (ei<strong>the</strong>r<br />

central or peripheral). Central<br />

suppression can extend ten degrees from<br />

<strong>the</strong> fovea. Worth four-dots, stereoscope<br />

tests, Bagolini lenses and <strong>the</strong> Nonius bars<br />

on <strong>the</strong> Mallett unit can be used to detect<br />

suppression. The Mallett unit also has<br />

specific test words; some of <strong>the</strong> letters are<br />

seen by both eyes and some by only <strong>the</strong><br />

left or <strong>the</strong> right. They are of increasing<br />

size and allow a measure of <strong>the</strong> degree<br />

of suppression.<br />

ARC (abnormal retinal<br />

correspondence) which is almost<br />

always HARC and can be termed a<br />

positive adaptation to <strong>the</strong> heterotropia<br />

and is described as where<br />

correspondence exists between areas<br />

of <strong>the</strong> retina on <strong>the</strong> fixating and<br />

deviating eye which receive <strong>the</strong> same<br />

image. The correspondence prevents<br />

<strong>the</strong> occurrence of diplopia and allows<br />

for a limited degree of stereopsis. ARC<br />

is examined by <strong>the</strong> use of a Bagolini<br />

lens placed before <strong>the</strong> non-fixing eye<br />

while <strong>the</strong> patient is fixating a spot light<br />

target; if <strong>the</strong> patient reports <strong>the</strong> streak<br />

of <strong>the</strong> Bagolini lens as being centred<br />

on <strong>the</strong> spot, ARC may be diagnosed. A<br />

distance Mallett unit can be used; if<br />

<strong>the</strong> patient sees that <strong>the</strong> Nonius lines<br />

are aligned when a heterotropia is<br />

present, <strong>the</strong>re is ARC.<br />



This condition exists when a nonfoveal<br />

point is used for fixation; since<br />

retinal sensitivity is reduced<br />

parafoveally, <strong>the</strong>re is always a reduced<br />

acuity measured in <strong>the</strong>se eyes which<br />

depends upon <strong>the</strong> degree of<br />

eccentricity of fixation. Assessment<br />

can be made with <strong>the</strong> eccentric<br />

fixation graticule of <strong>the</strong> direct<br />

ophthalmoscope while occluding <strong>the</strong><br />

o<strong>the</strong>r eye; <strong>the</strong> target is usually red-free<br />

to ensure <strong>the</strong> patient remains<br />

comfortable during <strong>the</strong> test. The<br />

fixation can be classified according to<br />

its state (steady or unsteady), position<br />

(superior, inferior, nasal or temporal)<br />

and by its size in degrees from <strong>the</strong><br />

centre of <strong>the</strong> fixation target.<br />

Management of BV anomalies<br />

• Diagnosis of anomaly<br />

• Recent or long-standing?<br />

• Aetiology<br />

• Management<br />

• Referral or next review<br />


1. Cashell, G.T.W. and Durran, I.M. (1980)<br />

‘Handbook of Orthoptic Principles 4th<br />

edition’. Churchill Livingstone, London.<br />

2. Stidwill, D. (1990) ‘Orthoptic Assessment<br />

and Management. Blackwell Science,<br />

London.<br />

3. Evans, B.J.W. (1997) ‘Binocular Vision<br />

Anomalies: Investigation and Treatment<br />

3rd edition’. Butterworth-Heinemann,<br />

Oxford.<br />

4. Scheimann, M. and Wick, B. (1994)<br />

‘Clinical Management of Binocular Vision,<br />

Heterophoric, Accommodative and Eye<br />

Movement Disorders’. Lippincott Raven,<br />

Philadelphia.<br />

5. Goss, D.A. (1995) ‘Ocular Accommodative,<br />

Convergence and Fixation Disparity. A<br />

Manual of Clinical Analysis 2nd edition’.<br />

Butterworth-Heinemann, Oxford.<br />

6. Birnbaum, M.H. (1993) ‘Optometric<br />

Management of Near-point Vision<br />

Disorders’. Butterworth-Heinemann,<br />

Oxford.<br />

7. Rowe, F. (1997) ‘Clinical Orthoptics’.<br />

Blackwell Science, London.<br />


For accommodative facility<br />

flipper bars without lenses, contact<br />

Paul Adler,<br />

50 High Street, Stotfold, Hitchin,<br />

Herts, SG5 4LL. Tel: 01462-732393<br />

Optometric Educators,<br />

PO Box 172, Bromley, Kent,<br />

BR2 OWZ. Tel: 0181-466 6535.<br />

Email: admin@optometrist.co.uk<br />

This is <strong>the</strong> second article in a<br />

series of five to be published, based on last<br />

September’s Optometric Educators<br />

lecture series entitled<br />

“Essential clinical skills for tomorrow’s patients”.<br />

36<br />


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