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Convergence excess accommodative esotropia: a descriptive

review of patients presenting over a period of 10 years

TESS GARRETTY DBO

Department of Orthoptics, St James University Hospital, Leeds

Abstract

Aim: Convergence excess accommodative esotropia

describes an esotropia on accommodation at near

fixation that is controlled to an esophoria/orthophor-

ia at distance fixation with binocular single vision.

Sixty-four cases have presented to the Leeds Teach-

ing Hospitals NHS Trust over the last 10 years. This

descriptive paper outlines the clinical characteristics

of this cohort of patients.

Methods: Information was reviewed regarding all

children diagnosed as having convergence excess

accommodative esotropia entered onto a departmen-

tal database between 1999 and 2009.

Results: Only 3 children complained of diplopia at

presentation. The mean refractive error of the group

was right þ2.90DS and left þ2.80DS. The median

angle of deviation was 25

D

BO at 1/3 m and 4

D

BO at

6 m. The mean Ac/A ratio using the gradient method

was 6:1 at 1/3 m and 10:1 at 6 m. The angle of

deviation was found to be altered by a period of

monocular occlusion and prism adaptation. Twenty

per cent of children required occlusion for amblyo-

pia. Nine per cent of those with convergence excess

were found to decompensate to constant esotropia

with time.

Conclusions: Testing distance, a period of monocular

occlusion and prism adaptation have been shown to

alter the angle of deviation and the Ac/A ratio in

convergence excess accommodative esotropia. Simi-

larities between convergence excess and fully accom-

modative esotropia are outlined.

Key words: Accommodative convergence to accom-

modation (Ac/A) ratio, Convergence excess esotropia

Introduction

The term ‘convergence excess esotropia’ defines an

esotropia that is greater at near fixation than distance and

was first described by Donders in 1864.

1,2

Much con-

fusion has been generated by the term through the years.

For some, it simply defines a constant esotropia greater

at near than distance with no evidence of binocular

single vision.

3

Others use it to define an esotropia at near

fixation with orthotropia at distance that can be further

categorised into accommodative, non-accommodative

and hypo-accommodative convergence excess.

4,5

This

study examines those with convergence excess accom-

modative esotropia – esotropia on accommodation at

near fixation that is controlled to an esophoria/ortho-

phoria at distance fixation with binocular single vision

(BSV) and a high Ac/A ratio.

1

Convergence excess

esotropia is differentiated from near esotropia by

examining the effect of þ3.00DS lenses on the near

angle of deviation. In near esotropia the near angle will

remain unchanged through the additional lenses, whereas

in convergence excess esotropia the near angle will be

significantly reduced – invariably resulting in binocular

single vision at near.

Following previous investigation by the author into

the influence of testing distance on the Ac/A ratio in

fully accommodative esotropia

6

where the testing

distance was found to affect the results, it was decided

to routinely assess the Ac/A ratio at 1/3 m and 6 m in

children with convergence excess esotropia to investi-

gate whether similar changes occurred in this cohort. As

the Ac/A ratio is frequently altered by a period of

monocular occlusion in intermittent exotropia,

7,8

it was

also decided to investigate the influence of occlusion on

the Ac/A ratio for this cohort of patients.

Previous departmental audit revealed poor surgical

success in cases of convergence excess esotropia, with

approximately one-third of patients remaining esotropic

post-operatively, one-third being successfully aligned

and the remaining third becoming consecutively exo-

tropic. It was thought that the variable surgical outcome

may be a result of not revealing the true angle of

deviation pre-operatively; therefore prism adaptation

was undertaken in those wishing to consider squint

surgery in an attempt to reveal the true angle of deviation

and improve surgical results. Also, during scrutiny of the

records of patients who had decompensated from

convergence excess esotropia to constant esotropia the

author observed a marked change in the distance angle

of deviation with time without extra-ocular muscle

weakness. It was postulated that this represented an

uncovering or decompensation of the true distance angle

of deviation due to changing fusional ability rather than

an actual change in muscle balance. This would also be

investigated with prism adaptation.

Sixty-four patients with accommodative convergence

excess esotropia have presented to Leeds Teaching

Hospitals NHS Trust over the last 10 years. This

descriptive paper will outline the presentation, charac-

teristics, treatment and outcomes of those children

presenting with convergence excess in Leeds.

Br Ir Orthopt J 2011; 8: 23–28

Correspondence and offprint requests to: Tess Garretty, Department

of Orthoptics, Chancellor Wing, St James University Hospital,

Beckett Street, Leeds LS9 7TF. e-mail: tess.garretty@leedsth.nhs.uk

Methods

Details of all children attending Leeds Teaching

Hospitals with a diagnosis of convergence excess

esotropia were prospectively entered onto a departmental

database at the point at which the diagnosis was made.

Differential diagnosis between near esotropia and

convergence excess was made before entering the patient

onto the database. This may have been at the first visit

following refractive correction or at any point during the

child’s subsequent attendance, for example at a change

in diagnosis. The database is updated at each clinic

appointment. All orthoptic investigations entered onto

the database were achieved by a standardised testing

protocol and were performed in the vast majority of

cases by the author, with a small amount of data being

provided by two other very experienced examiners. All

data used for measuring the Ac/A ratio were performed

by the author using a strict testing protocol.

Sixty-four children (35 female, 29 male) attending

with convergence excess esotropia were identified from

the database and the following information was

gathered: age at presentation, signs/symptoms at pre-

sentation, duration of signs/symptoms, refractive error

and initial diagnosis after correction of refractive error,

angles of deviation, strength of BSV, change in

diagnosis, etc. The angle of deviation was measured

using the prism and cover test at 1/3 m and 6 m and the

presence of microtropia and necessity for occlusion was

examined. The Ac/A ratio was measured using the

gradient method at 1/3 m and 6 m. Treatment prescribed

and binocular outcomes were collated. All children

included in this study had undergone cycloplegic

refraction, full refractive correction was issued in all

cases and any spectacles issued were worn full time.

Results

Age at presentation

The mean age at presentation was 3 years 11 months

(median 4 years, range 1 year 1 month to 9 years 1

month). The mean duration of signs/symptoms prior to

presentation was 8.5 months (median 6 months, range 3

weeks to 48 months).

Signs and symptoms at presentation

Fourteen patients did not have a record of presenting

signs in the hospital notes (3 of whom had been referred

from other hospitals). Of the remaining 50 patients,

38 had a history of intermittent esotropia and 12 patients

had a history of constant esotropia. Only 3 children

volunteered symptoms of diplopia at presentation.

Initial diagnosis

Of the 64 children who, after refractive correction,

subsequently met the criteria for convergence excess

accommodative esotropia at presentation (before refrac-

tive correction) the provisional working diagnosis was:

Convergence excess esotropia: 22 (34%)

Constant esotropia: 18 (28%)

Non-specific intermittent esotropia/decompensating

esophoria: 16 (25%)

Esophoria: 1 (2%)

No squint detected: 1 (2%)

Esotropic at near but distance cover test was not

possible: 1 (2%)

Information not available: 5 (8%)

Refractive error

Sixty-one (95%) children were issued spectacles for full-

time wear. The full prescription was issued in all cases.

Hypermetropia 5þ1.00DS was corrected due to the

esotropia. Correction of myopia and astigmatism was

issued related to visual acuity. The mean spherical

equivalent following cycloplegic refraction was: right

þ2.90DS (median þ2.50 range 0.25 to þ7.50), left

þ2.80DS (median þ2.50, range 0.25 to þ7.00).

Diagnosis after refractive correction

Two months after refractive correction/adaptation the

diagnoses were:

Convergence excess esotropia: 36 (56%)

Fully accommodative esotropia: 13 (20%)

Constant esotropia: 9 (14%)

Non-specific intermittent esotropia: 1 (2%)

Too young for distance assessment: 1 (2%)

No abnormality detected: 1 (2%)

Information unavailable: 3 (5%)

All these patients subsequently met the criteria of

convergence excess esotropia following a further period

of time. Details are given in the section ‘Progression of

esotropia’.

Angle of deviation

Full refractive correction was worn and an alternate

prism and cover test was performed whilst the child

named pictures or letters of the smallest size discernible

to each eye (Fig. 1). The median angle of deviation at

1/3 m was 25

D

BO (SD 12

D

, range 12

D

to 65

D

). The

median deviation at 6 m was 6

D

BO (SD 5.5

D

, range 0

D

to 20

D

).

Ac/A ratio

The Ac/A ratio was measured using the gradient method

in 57 patients at 1/3 m and at the same visit in 48

children at 6 m. The full refractive correction was worn.

In an attempt to control accommodation the child was

asked to name pictures or letters of the minimum size

viewable by each eye whilst the measurements were

undertaken with and without the 3.00DS lenses. If the

3DS lenses were not cleared with each eye, the patient

was excluded from the results. After sufficient time,

encouragement and explanation, all those tested were

able to clear the þ3.00DS lenses at 1/3 m. One child was

not able to clear the 3.00DS lenses at 6 m. Details of

those measured at 1/3 m and 6 m are found in Fig. 2. At

1/3 m the mean Ac/A ratio was 6:1 (SD 3:1, range

1.7:1 to 13.3:1). At 6 m the mean Ac/A ratio was 10:1

(SD 3.7:1, range 2:1 to 17.7:1). The mean difference in

24 T. Garretty

Br Ir Orthopt J 2011; 8

the Ac/A ratio subtracting the 1/3 m from 6 m results

was 4.9:1 (SD 3.6). The Ac/A ratio was significantly

greater at 6 m than at 1/3 m (paired t–test, p<0.001,

95% CI 3.89 to 5.97).

Ac/A ratio following occlusion

Ten children underwent re-measurement of the deviation

following a 30 m in period of monocular occlusion as

part of a previously reported study.

6

Following occlusion

there was a change in the angle of deviation at 1/3 m of

between 5

D

and þ25

D

. At 6 m the change ranged from

12

D

to þ21

D

. Following occlusion, a change in the

Ac/A ratio of 2:1 or more was found in 7 patients at

1/3 m with 2 of these demonstrating a change of more

than 4:1. Similarly, 6 of the 10 cases changed by 2:1 or

more at 6 m with 2 of them changing by more than 4:1.

Whilst these changes do not reach statistical significance

(change in near Ac/A ratio: paired t-test, p¼0.557, 95%

CI 11.8 to 6.8; change in distance Ac/A ratio: paired

t-test, p¼0.200, 95% CI 11.8 to 2.8), there is a clear

clinical significance in many of the cases.

Prism adaptation

Prism adaptation (PAT) was undertaken in 21 patients

considering squint surgery. Criteria for consideration for

surgery were the inability to control the deviation

following treatment with bifocals or orthoptic exercises,

or parental choice to discontinue bifocal wear. The near

angle of deviation was fully corrected with Fresnel

prisms that were split equally between the two eyes and

the patient was reviewed 1 or 2 weeks later. The mean

age at time of PAT was 7.2 years (range 4.42–9.25

years). Each patient tolerated the prisms well. The mean

change in angle of deviation at 1/3 m following PAT

Fig. 1. Cases sorted by near angle of deviation. Top of bar represents near angle of deviation, bottom of bar represents distance angle of

deviation (prior to prism adaptation).

Fig. 2. Cases sorted by mean Ac/A ratio. The mean is denoted by the dot ([ratio 1/3 m þratio 6 m ]/2). For all patients except numbers 5 and 20

(black filled bars), the top of the bar represents the Ac/A ratio at 6 m and the bottom of the bar represents the Ac/A ratio at 1/3 m. Patients 5 and 20

had a near Ac/A ratio that exceeded the distance Ac/A ratio, therefore the top of the bar denotes the near ratio and the bottom of the bar the distance

ratio.

Convergence excess accommodative esotropia: 10-year review 25

Br Ir Orthopt J 2011; 8

was 18.5

D

(SD 12.1

D

, range 10

D

to þ35

D

) This was

statistically significant (paired t-test, p<0.001, 95% CI

15

D

to 26

D

). At 6 m the mean change in deviation was

17.5

D

(SD 10.9

D

, range 2

D

to þ36

D

). Again this was

statistically significant ( p<0.001, 95% CI 16

D

to 27

D

).

Bifocals

Thirty-seven patients were issued bifocal spectacles as a

primary treatment; 4 additional children were issued

bifocals post-operatively. The minimum additional plus

lens that produces esophoria with reasonable fusion and

stereopsis is prescribed initially. The mean age at issuing

bifocals as a primary treatment was 63 months (SD 17

months, range 23 to 109 months). The mean length of

time wearing bifocals was 32 months (SD 29, range 3 to

113 months). Some of these children are still wearing

bifocals so the length of wear data are not complete. Six

of the 37 children appeared to be successfully weaned

from the bifocals; however, 3 of these children decom-

pensated between 6 and 8 months later and required

further intervention. Two children were discharged

wearing bifocals. Nineteen of the 37 children treated

initially with bifocals went on to have (or be listed for)

surgery once it was shown that it was not possible to

reduce the bifocal addition further without inducing a

manifest deviation at near.

Microtropia

Nine (14%) children had a microtropia confirmed by

fixation examination. Of these, only 4 had anisometropia

of 1.25DS or more. Seven further children had suspected

microtropia (evidenced by 4

D

prism test) but not

confirmed by fixation examination.

Occlusion

Thirteen (20%) of the 64 were prescribed occlusion

therapy for amblyopia. Six of these had a confirmed

associated microtropia, 4 had a suspected microtropia

and the remaining children had normal central fixation.

Progression of esotropia

The 13 children initially diagnosed with fully accom-

modative esotropia following refractive correction con-

trolled the deviation at near whilst wearing the

spectacles for a mean period of 20 months before a

manifest deviation at 1/3 m was first seen (median 16,

SD 11, range 2 to 35 months). The mean spherical

equivalent refractive error for this group was þ3.60DS

(range þ1.00DS to þ7.00DS). The median age at

decompensation from fully accommodative esotropia to

convergence excess accommodative esotropia was 58

months (mean 59, SD 11, range 39–75 months).

Six (9.8%) children spontaneously decompensated

from convergence excess esotropia to a constant

esotropia. Of these 6, following initial refractive

correction, 3 had convergence excess accommodative

esotropia immediately, 1 had remaining constant eso-

tropia for 2 months before settling to convergence excess

accommodative esotropia and 2 children had controlled

to a fully accommodative esotropia for 14 and 15 months

before losing control of the deviation at near. The angle

of deviation at 6 m was seen to change considerably

over this time. Details are given in Table 1. Four of these

6 children complained of diplopia at 6 m when manifest.

Surgery

Twenty-eight children have undergone squint surgery

during the 10 years of data collection. Twenty underwent

bilateral medial rectus (MR) recessions, 1 of whom also

had bilateral inferior oblique myectomies. Five had

single MR recession, 2 underwent unilateral MR

recession with lateral rectus resection and 1 had a Faden

posterior fixation suture to one MR. Since mid-2007, all

children (n¼17) undergoing squint surgery have under-

gone pre-operative prism adaptation.

Discussion

The characteristics of convergence excess accommoda-

tive esotropia are described in Ansons and Davis’ book

Diagnosis and Management of Ocular Motility Dis-

orders.

1

The age at presentation and degree of refractive

error found in the present study relate well to those

quoted. Ansons and Davis state that the Ac/A ratio ‘often

exceeds 8:1’. In this study 14 (25%) of the 57 children

tested at 1/3 m had an Ac/A ratio of at least 8:1 as did

36 (75%) of the 48 tested at 6 m.

Ansons and Davis state that presentation of conver-

gence excess accommodative esotropia is usually

between 2 and 5 years of age. This study found the

age of presentation to be between 2 and 9 years. The

anecdotal clinical impression is that accommodative

esotropia will tend to manifest itself when the child

begins to really exert accommodation when becoming

interested in fine detail. One would expect accommoda-

tive effort to be truly exercised when the child starts

school at the age of 5 years; therefore an upper age for

presentation of this degree would be expected. However,

the intermittent nature of this type of strabismus and the

lack of diplopia means that the age at presentation will

be dependent not only on the observations of family and

teachers – the deviation may have been present for some

Table 1. Change to 6 m angle of deviation following spontaneous decompensation to constant esotropia

Patient no. Age at decompensation

(years)

Time after presentation

(months)

Diplopia 6 m pre-decompensation

angle (prism dioptres)

6 m post-decompensation

angle (prism dioptres)

1 6.75 13 No 6 30

2 7.25 33 Yes 4 25

3 8.3 62 Yes 10 30

4 8.9 26 Yes 4 16

5 5.3 27 No 6 20

6 7.3 76 Yes 6 16

26 T. Garretty

Br Ir Orthopt J 2011; 8

time before being noticed – but also their motivation to

seek a medical opinion. Of course it is also feasible that

the deviation in these older children actually manifested

itself at an older age.

This paper has outlined the progression of conver-

gence excess esotropia. Some of the patients included in

this study initially behaved as fully accommodative

esotropes for some time before their vision broke down

at near to convergence excess esotropia. Interestingly,

the mean age that this decompensation generally

occurred was around the age when children start school

in the UK. A small number of these children with

convergence excess esotropia then further decompen-

sated to become constant esotropes. This occurred at a

slightly older age, with the youngest being just over 5

years of age and the oldest being nearly 9. The

decompensation of accommodative esotropia has been

documented by others. Vivian

5

reported an increase in

the near deviation in patients presenting initially with

fully accommodative esotropia in 6–11% of cases and

Dickie and Scott

9

reported that 13% of 114 patients with

fully accommodative esotropia deteriorated to lose

binocularity despite good compliance with spectacle

wear. They found that the decompensation occurred at a

mean age of 7.6 years (range 3.8 to 13.3 years) and was

not related to Ac/A ratio. The age at decompensation

was therefore slightly older in their study than in this

present study. Dickie and Scott’s study described the

decompensation as ‘total’, i.e. the child decompensated

at 1/3 m and 6 m not to a convergence excess esotropia.

However, Dickie and Scott, in this American study, also

state that ‘almost all of the patients had at least

peripheral fusion’ prior to decompensation. This would

imply that not all of their included patients would be

categorised as true fully accommodative esotropes in the

UK.

Havertape et al.

10

compared different methods of

measuring the Ac/A ratio in accommodative esotropia

and found that using 3.00DS lenses at 6 m fixation

revealed a higher Ac/A ratio than using þ3.00DS lenses

at 1/3 m. Gage

11

examined the Ac/A ratio using the

gradient method at 1/3 m and 6 m in a small group of

esophoric and exophoric subjects and found that there

was no statistical difference in outcome using the two

methods in esophoria (although 2 subjects showed a

change of 9:1 and 10:1 which would certainly be

considered clinically significant); she also found that

those with exophoria had a slightly reduced Ac/A ratio

on distance fixation. A study by this author of the Ac/A

ratio in fully accommodative esotropia

6

found that the

testing distance did not influence the Ac/A ratio in a

control group of subjects with small, well-compensated

heterophoria (mean 2.2:1 at 1/3 m and 2.9:1 at 6 m ), but

in those with fully accommodative esotropia the Ac/A

ratio was significantly larger when measured at 6 m

(mean 9:1) than when measured at 1/3 m (mean 4:1).

This present study similarly demonstrates the signifi-

cance of testing distance when measuring the Ac/A ratio

in convergence excess esotropia: the measure of the

Ac/A ratio at 6 m exceeded the near ratio in 39 (81%) of

48 cases. Therefore it would appear that the testing

distance used for measuring the Ac/A ratio has little

influence on the results in small heterophoria but that in

accommodative esotropia, both fully accommodative

and convergence excess, the distance gradient method

reveals a significantly larger result than the near

method. It is feasible that the effort to accommodate

through concave lenses at 6 m fixation results in a

different (and perhaps more accurate) accommodative

response from that when asking a patient to relax their

accommodation through convex lenses at 1/3 m.

The effect of target size on the angle of deviation at

1/3 m and 6 m was also outlined in this author’s fully

accommodative esotropia study.

6

The paper compared

the angle of deviation at 1/3 m and 6 m measured with

the patient viewing a 6/60 and 6/6 target and, perhaps not

surprisingly, demonstrated that the angle of deviation

increased when viewing a 6/6 target compared with a

6/60 target in fully accommodative esotropia.

All the papers mentioned have measured the stimulus

Ac/A ratio. It cannot be assumed that viewing a detailed

target through plus and minus lenses will elicit an

accommodative response exactly equal to the strength of

the lens used. Dynamic retinoscopy would reveal the

accuracy of accommodation in these children but few

UK orthoptists currently have the skills to undertake this

procedure. (Three children included in this study under-

went dynamic retinoscopy with the hospital optometrist

and showed accurate accommodative responses to a

detailed target at 1/3 m. However, due to the small

numbers tested, details are not included in the results.)

Instructing the patient to read small letters whilst

measurements are undertaken attempts to ensure that

accurate accommodative change occurs in the clinical

environment.

The usefulness of the stimulus Ac/A ratio as a

diagnostic tool and its use in surgical planning should

perhaps be re-considered. Many papers have outlined the

differences in stimulus and response ratios

12–14

and this

paper has outlined changes to the angle of deviation

resulting from differing target size, fixation distance,

prism adaptation and occlusion. These effects will affect

the Ac/A ratio results. The number of factors influencing

the measure of the Ac/A ratio means that the results will

vary considerably depending on the testing regime

adopted. Unless strict protocols in testing regimes are

undertaken, the results are likely to be so variable as to

render them of little diagnostic value. The size of the

deviation following prism adaptation (or to a lesser

extent following a period of monocular occlusion) is

likely to be of more value when planning management of

convergence excess esotropia than the actual Ac/A ratio.

It is no longer routine practice to measure the Ac/A ratio

in convergence excess within the department in Leeds.

This paper has demonstrated the close relationship

between convergence excess and fully accommodative

esotropia. The mean refractive error in this author’s fully

accommodative esotropia study

6

was þ4.30DS (range

þ2.00DS to þ8.00DS); the mean refractive error within

this present study of convergence excess esotropia was

þ2.90DS (range 0.25 to þ7.50). The Ac/A ratio is

often high in both categories of strabismus. The fully

accommodative esotropia study

6

split the subjects into

two groups: those who learnt to control the deviation

without the spectacles with time and those who did not.

The study found that the group with fully accommoda-

Convergence excess accommodative esotropia: 10-year review 27

Br Ir Orthopt J 2011; 8

tive esotropia who did not learn to control the deviation

without spectacles had mean Ac/A ratios of 2.6:1 at

1/3 m and 9:1 at 6 m. This study of convergence excess

accommodative esotropia found a higher mean Ac/A of

6:1 at 1/3 m but a similar Ac/A of 10:1 at 6 m. A

proportion of children with fully accommodative eso-

tropia are seen to decompensate to convergence excess

over time, further linking these two conditions. It is

proposed that convergence excess esotropia and fully

accommodative esotropia are not truly distinct entities

but represent different points on a spectrum of the same

condition.

Horwood

15

has described the various drivers to

accurate vergence (blur, accommodation, proximity,

disparity) and has reported that disparity is the main

driver for accurate vergence in most non-squinting

individuals. Perhaps these main drivers are different in

the sub-categories of intermittent strabismus? Maybe

those hypermetropes who develop esotropia have

vergence that is more driven by accommodation than

those who remain fully binocular? Perhaps those who

develop convergence excess esotropia have even more

accommodative drive than those who develop fully

accommodative esotropia? As yet we do not have

knowledge of the drive to vergence in differing

categories of strabismus.

Treatment of convergence excess esotropia with

bifocals has produced limited success for the children

in this cohort. Bifocals are routinely prescribed within

the department as a first-line treatment. The minimum

additional plus lens that produces esophoria with

reasonable fusion and stereopsis is prescribed initially.

The aim is to endeavour to reduce the addition by

0.50DS every 6 months (departmental guideline). If

the deviation was not controlled with the reduced

additional lens, the parents were given the option of

increasing the addition again or considering surgery. It is

the author’s experience that reducing the bifocal addition

down to þ1.00DS is usually uncomplicated, but weaning

the child from this small additional lens is often

unsuccessful even with the addition of orthoptic

exercises. Stewart and Scott

16

reported similar difficul-

ties. Forty-three per cent of those with convergence

excess wearing bifocals became ‘bifocal failures’ – the

deviation increased beyond the patient’s fusional

capabilities during their bifocal treatment. Parents in

Leeds are now counselled that bifocals are prescribed to

maintain comfortable BSV until such time as accurate

prism and cover test measurements are possible and

prism adaptation can be undertaken. At this point

surgery is planned.

Prism adaptation or a period of monocular occlusion

may reveal a hidden large angle of deviation at 6 m in

convergence excess accommodative esotropia that has

been shown to decompensate to constant esotropia over

time in a small group of patients. It is postulated that

tenacious fusion masks the true distance angle of

deviation in many patients with convergence excess in

a similar way as described by Kushner

7

and Rosenfield

et al.

8

in intermittent exotropia. The author’s previous

paper investigating convergence excess esotropia

17

suggested two subcategories of convergence excess

accommodative esotropia:

.True convergence excess: Esotropia at 1/3 m with a

small well-controlled esophoria at 6 m. No signi-

ficant increase in the distance angle of deviation

following a period of monocular occlusion or prism

adaptation.

.Simulated convergence excess: The esophoria at

6 m increases significantly following occlusion or

prism adaptation.

The paper postulated that sub-categorisation of this

condition may influence its management. Those with

true convergence excess may be at risk of consecutive

distance exotropia following surgery and are possibly

best managed with long-term bifocal use. Those with

simulated convergence excess pose a low risk of

consecutive exotropia and more aggressive surgery can

be proposed. These patients may be at a greater risk of

decompensating to constant esotropia over time.

Clinicians should be aware of the effect of fixation

target size and the testing distance on the results of prism

and cover test and consequently on the Ac/A ratio, and

should consider a period of monocular occlusion or

prism adaptation to reveal the true angle of deviation

before planning surgical interventions.

References

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Motility Disorders, 3rd edition. Oxford: Blackwell Science, 2001:

chapt 12.

2. Donders FC. On the Abnormalities of Accommodation and

Refraction of the Eye. London: The New Sydenham Society,

1864.

3. Wygnanski-Jaffe T, Trotter J, Watts P, Kraft S, Abdolell M. Pre-

operative prism adaptation in acquired esotropia with convergence

excess. J AAPOS 2003; 7: 28–33.

4. Arnoldi KA. Convergence excess: characteristics and treatment.

Am Orthopt J 1999; 49: 37–47.

5. Vivian AJ, Lyons CJ, Burke J. Controversy in the management of

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