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Convergence Excess Esotropia: a descriptive review of patients presenting over a period of 10 years


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Aim: Convergence excess accommodative esotropia describes an esotropia on accommodation at near fixation that is controlled to an esophoria / orthophoria at distance fixation with binocular single vision.1 Sixty four cases have presented to The Leeds Teaching Hospitals NHS Trust over the last 10 years. This descriptive paper outlines the clinical characteristics of this cohort of patients. Method: Information regarding all children diagnosed as convergence excess accommodative esotropia entered onto a departmental database between 1999 and 2009 was reviewed. Results: Only three children complained of diplopia at presentation. The mean refractive error of the group was right +2.90DS and left +2.80DS. The median angle of deviation was 25ΔBO at 1/3m and 4ΔBO at 6m. The mean Ac/A ratio using the gradient method was 6:1 at 1/3m and 10:1 at 6m. The angle of deviation was found to be altered by a period of monocular occlusion and prism adaptation. Twenty percent of children required occlusion for amblyopia. Nine percent of those with convergence excess were found to decompensate to constant esotropia with time. Conclusion: Testing distance, a period of monocular occlusion and prism adaptation has been shown to alter the angle of deviation and the Ac/A ratio in convergence excess accommodative esotropia. Similarities between convergence excess and fully accommodative esotropia are outlined.
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Convergence excess accommodative esotropia: a descriptive
review of patients presenting over a period of 10 years
Department of Orthoptics, St James University Hospital, Leeds
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
BO at 1/3 m and 4
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
The term ‘convergence excess esotropia’ defines an
esotropia that is greater at near fixation than distance and
was first described by Donders in 1864.
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.
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.
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.
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
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,
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:
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.
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
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
BO (SD 12
, range 12
to 65
). The
median deviation at 6 m was 6
BO (SD 5.5
, range 0
to 20
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.
Following occlusion
there was a change in the angle of deviation at 1/3 m of
between 5
and þ25
. At 6 m the change ranged from
to þ21
. 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
Convergence excess accommodative esotropia: 10-year review 25
Br Ir Orthopt J 2011; 8
was 18.5
(SD 12.1
, range 10
to þ35
) This was
statistically significant (paired t-test, p<0.001, 95% CI
to 26
). At 6 m the mean change in deviation was
(SD 10.9
, range 2
to þ36
). Again this was
statistically significant ( p<0.001, 95% CI 16
to 27
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.
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
prism test) but not
confirmed by fixation examination.
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.
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.
The characteristics of convergence excess accommoda-
tive esotropia are described in Ansons and Davis’ book
Diagnosis and Management of Ocular Motility Dis-
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
Time after presentation
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
reported an increase in
the near deviation in patients presenting initially with
fully accommodative esotropia in 6–11% of cases and
Dickie and Scott
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
Havertape et al.
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
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
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.
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
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
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
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
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
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
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
and Rosenfield
et al.
in intermittent exotropia. The author’s previous
paper investigating convergence excess esotropia
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
.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.
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... This was first described by Donders. 1 Much confusion has been generated by its definition through the years. 2 An acceptable definition of convergence excess esotropia would be a convergent squint, which is .8 prism diopter (PD) and is greater for near fixation than distance fixation after full hypermetropic correction. ...
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Purpose To compare and evaluate the efficacy of two different surgical techniques for the treatment of near-distance disparity esotropia; combined resection–recession and recession–retroequatorial myopexy of medial rectus muscles. Patients and methods This prospective study included 28 patients diagnosed with convergence excess esotropia who had worn their full cycloplegic refraction and/or bifocal glasses for at least 6 months and still had near-distance disparity esotropia. The patients were divided into 2 groups; Group I underwent combined bimedial rectus muscles resection 2.5 mm from the insertion end with recession based on near-angle esotropia according to current surgical tables with 1 mm add of recession for each muscle, while Group II underwent bimedial recession based on far angle combined with retroequatorial myopexy at 13–14 mm from insertion. A satisfactory result was defined as orthophoria or esotropia <10 prism diopters (Δ) at near and distance with reduction of the near-distance disparity to <10 Δ. The patients were followed up for at least 2 years for stability of correction and late onset consecutive exotropia. Results In Group I, all the patients had satisfactory alignments at near and far with residual near–far disparity #10 Δ, no cases of overcorrection at far was reported; while in Group II, all cases had orthophoria at far, but 4 cases (28.6%) showed near–far disparity >10 Δ. Conclusion The technique of combined resection–recession is safe, easy and more effective in the treatment of near-distance disparity esotropia regardless of the level of accommodative convergence/accommodation ratio, with stability of results though longer follow-up period is still needed.
Nonrefractive accommodative esotropia (NRAET) is a form of pediatric acquired strabismus in which the accommodative convergence to accommodation (AC/A) ratio is high. Accordingly, the near angle of esotropia is notably greater than the distance angle, and after full-cycloplegic correction, the near angle is not fully resolved. Nonsurgical plans to deal with convergence-excess esotropia include observation only and single vision lenses with or without a ground-in plus addition power. Bifocals and progressive addition lenses (PALs) are two available designs when the preferred management approach is near plus addition. There are inconsistent data regarding the practical effectiveness of these two optical modalities in providing ocular alignment. Several studies advocated using bifocals and PALs as the primary management strategy in patients with NRAET; however, because of developmental concerns, others affirm that early surgical intervention can be a more conservative strategy than optical treatment. They noted that this method might be ineffective or even pernicious due to the need to procrastinate the surgical intervention. In practice, the prescription of near plus addition lenses in the two forms of bifocals and PALs could be a double-edged sword in the treatment course of patients with NRAET. Therefore, an individualized approach according to the age, degree of refractive error, AC/A ratio, esotropia angle at distance and near, amblyopia coexistent, and parents’ economic and cosmetic concerns would be rationale before choosing any treatment option.
Convergence excess esotropia describes a heterophoria with binocular single vision (BSV) on distance viewing that becomes esotropic on accommodation upon near fixation. Prism adaptation test (PAT) is a procedure routinely used to reveal the maximum angle of deviation preoperatively for many types of strabismus and has been shown to improve surgical outcomes; however, it is not conventionally used for convergence excess esotropia. Aim: This study compares the angle of deviation at 1/3 m and 6 m before and after prism adaptation in subjects with convergence excess esotropia to determine if a masked distance angle of deviation can be demonstrated similar to the masked near angle of deviation in some intermittent exotropes. Surgical results are reported. Results: Fifty-eight children with convergence excess esotropia were prescribed prism adaptation prior to strabismus surgery and 49 met the inclusion criteria. A median increase in the angle of deviation of 20 prism dioptres (PD) was seen at both 1/3 m and 6 m following PAT. These changes were statistically significant (p < 0.001) at both distances. Following one surgical procedure, 83.6% were fully binocular postoperatively. Conclusion: Prism adaptation frequently reveals an otherwise masked large distance angle of deviation in convergence excess esotropia. Convergence excess esotropia can be subdivided into two categories: true and simulated. Those with true convergence excess exhibit a manifest convergent strabismus when viewing a close object and a small, well-controlled latent strabismus upon fixation of a distant object. Those with simulated convergence excess have a comparable near deviation to those with true convergence excess but can be shown to have a distance deviation that approaches the size of the near strabismus once the normal fusional mechanisms are disrupted by a period of prism adaptation.
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The gradient stimulus and heterophoria stimulus measures of the accommodative convergence/accommodation (AC/A) ratio are simple and widely-used techniques. We compared these two clinical methods with the more accurate and objective gradient response AC/A ratio method. Twenty-three subjects, with ages ranging from 17 to 42 years and with normal binocular vision, were assessed. The response AC/A ratio was determined using a Canon AutoRef R-l to measure accommodation and an IRIS eye movement monitor to measure eye movements. Stimulus AC/A ratios were determined by taking phoria measures with the presentation of lenses (gradient method) and by varying the working distance (heterophoria method), with the accommodation taken as dioptric value of each stimulus. The mean AC/A ratios were 4.37 ± 1.31 ΔA/D (mean ± standard deviation), 3.49 ±2.17 Δ/D, and 5.81 ± 1.03 Δ/D, for the gradient response, gradient stimulus and heterophoria stimulus AC/As, respectively. The gradient stimulus AC/A showed only moderate validity, as measures corresponded with the ratios of the response method mainly when identifying very high and very low AC/A ratios (r2= 0.388). Inaccuracies in the gradient stimulus AC/A arose because the accommodation often varied markedly from the value of the stimulus lenses. The heterophoria stimulus AC/A appeared to be invalid for the subjects tested, as no correlation was evident between it and the response AC/A (r2= 0.003). Since the heterophoria technique is susceptible to both errors of focus and the influence of proximal vergence, it may reliably detect only very high AC/A ratios. (Clin Exp Optom 1995; 78: 1: 3–10)
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Objective infrared recording devices were used to measure simultaneously and continuously both accommodation and accommodative vergence to near stimuli in 4 subjects with intermittent exotropia of the divergence-excess type (2 simulated and 2 true). In addition standard clinically determined stimulus accommodative convergence to accommodation (AC/A) ratios were measured. Results showed the mean group response AC/C ratio to be 5.9/1 (range 4.5-8.0/1) with no differences between true and simulated divergence-excess. Similar AC/A ratios were found after 45 minutes of monocular occlusion. Our results clearly demonstrate relatively normal response AC/A ratios in these subjects. Thus, contrary to what is believed by many clinicians, the reduced ocular deviation at near compared with distance vision cannot be attributed primarily to an abnormally high AC/A ratio. We believe than fusional convergence after-effects and/or proximal convergence effects contribute to inflate the clinically determined stimulus AC/A ratios.
Bifocal glasses are a common form of therapy for accommodative esotropia with a high AC/A ratio. Patients who respond to bifocal therapy show a reduced deviation with fusion, when using the bifocal. A retrospective study of patients who were initial bifocal responders was undertaken. Patients were divided into two groups: Group 1 (25 patients) were bifocal successes, in whom fusion was maintained over time and the bifocals were discontinued. Group 2 (19 patients) were bifocal failures, in whom fusion was lost, esotropia increased, and surgery was required. The purpose of this paper was to determine patient characteristics that can be used to identify those who may deteriorate and require surgery, and to determine the incidence of deterioration. A statistically significant difference was found, at the .05 level by the t-test, in the initial refractive error of groups 1 and 2. A statistically significant difference was also found, at the .001 level by the t-test, in the amount of distance deviation at onset of bifocal therapy.
This comprehensive, clinically-grounded textbook, now in its fourth edition, supports orthoptists and ophthalmologists in decision-making through the patient care process, from presentation to discharge. Written by authors with extensive experience in teaching and research, Diagnosis and Management of Ocular Motility Disorders offers a clear and practical overview of assessment and management principles and further explores the clinical features of specific disorders, from amblyopia and infantile strabismus to supranuclear and infranuclear disorders, as well as other miscellaneous disorders of ocular movement. A brand new chapter on congenital cranial dysinnervation disorders reflects recent advances in gene mapping and increased understanding of this condition, and a new appendix provides surgical dose tables for easy reference. Now in full colour throughout, with additional diagrams and photographs of surgical techniques, this remains the key reference text for orthoptic and ophthalmic professionals managing patients with eye movement disorders. © 2014 by John Wiley & Sons, Ltd. 1986, 1991, 2001 by Blackwell Science Ltd, a Blackwell Publishing company. All rights reserved.
Convergence excess esotropia may result from a high AC/A ratio (accommodative convergence excess), abnormally high proximal convergence (non-accommodative convergence excess), or decreased accommodative amplitudes (hypoaccommodative convergence excess). To distinguish between the three, the gradient AC/A ratio must be calculated, and the accommodative amplitudes measured. Of 77 consecutive patients with a distance-near disparity of ≥ 10Δ, 51% had a high AC/A ratio (mean 8:1) and normal accommodative amplitudes, 48% had a normal AC/A (mean 3:1) and normal accommodative amplitudes, and 1% had normal AC/A and low accommodative amplitudes. There was no correlation between the magnitude of the distance-near disparity and the AC/A ratio. Convergence excess secondary to high AC/A ratio initially responded well to bifocals, though most eventually required surgery due to deterioration of the strabismus angle, bifocal intolerance, or inability to wean from the bifocal power. Non-accommodative convergence excess was managed surgically, and hypoaccommodative convergence excess was treated with spectacles.
Convergence excess esotropia defines an esotropia on accommodation at near fixation with binocular single vision and motor fusion at distance fixation associated with a high accommodative convergence: accommodation (Ac/A) ratio. The effect of occlusion on exotropia has been well described and is known to alter the Ac/A ratio. This study examines the effect of monocular occlusion on convergence excess esotropia. The Ac/A ratio was measured using the gradient method at 1/3 and 6 m in 10 patients with convergence excess esotropia immediately prior to and following a 30-minute period of monocular occlusion. Clinically and statistically significant differences to the angle of deviation and the Ac/A ratio were found in some patients following occlusion. Ac/A ratio measurement in convergence excess esotropia is influenced by fusional tenacity. Disrupting this fusion with a period of monocular occlusion results in changes to the angle of deviation in some patients, suggesting subcategorization of this condition into true and simulated convergence excess esotropia. Measurements of the Ac/A ratio are influenced by fixation distance.
A number of patients with accommodative esotropia who are initially well controlled in their spectacle correction will deteriorate. To obtain an overall estimate of the prevalence of deterioration and to examine the associated clinical features for an indication of which factors may influence deterioration, 114 charts of patients with the diagnosis of accommodative esotropia, who were followed for a period of at least 10 years, were reviewed. Results of this review showed that 15 of the 114 patients (13%) deteriorated. Overall, 73 patients had a normal AC/A ratio (viz less than 5:1 by the gradient method) and 41 patients had a high AC/A ratio; deterioration occurred in statistically identical proportions in each group. There was an increasing frequency of deterioration the longer the delay between the onset of esodeviation and prescription of optical correction. In addition, deterioration was found to be most prevalent in patients for whom the age of onset was 24 months or younger. Other parameters were consistent with features typically reported in cases of accommodative esotropia.
The two most commonly used clinical methods of determining a high AC/A ratio are: 1) the gradient method, and 2) the distance/near disparity method. Significant differences can be found not only between these two methods, but also in the different techniques for the gradient method alone. The purpose of our study is to compare the gradient method using +3.00 lenses for near and -3.00 lenses for distance, and the distance/near disparity method. Patients examined over a 2-year period (1995-1997) with a high AC/A ratio esotropia according to the distance/near disparity were grouped according to level of high AC/A ratio, then prospectively measured by the gradient method (using plus lenses for near and minus lenses for distance). All measurements were performed with full spectacle correction in place according to cycloplegic refraction, and with fixation on an accommodative target. Forty-five patients were included. Using both plus and minus lenses, a high AC/A ratio by the gradient method was found in 16 (36%) patients, (2 [12%] with a grade 1; 7 [44%] with a grade 2; and 7 [44%] with a grade 3, by the distance/near disparity method), a normal ratio was found in 6 (13%), and no patient had a low ratio. Twenty-three patients fell into a different category of AC/A ratio using plus lenses for near compared with minus lenses for distance. The distance/near disparity method appears to diagnose a high AC/A ratio much more frequently than the gradient method. There was some variability in the AC/A ratio with plus versus minus lenses when the gradient method was used. Further study using the gradient method in patients without a significant distance/near disparity is required.
The accuracy of the gradient technique for measuring the clinical accommodative convergence to accommodation (AC/A) ratio is dependent upon obtaining veridical heterophoria measurements. However, previous studies have demonstrated that the sustained output of slow fusional vergence, which may take several minutes or even hours to decay, can bias heterophoria assessment. In the clinical setting, it is usual to estimate the AC/A ratio after just a few seconds of dissociation. This study investigated whether the slow fusional vergence response alters this crosslink ratio by comparing values of AC/A measured both before and immediately after a 1-hr period of continuous monocular occlusion. Sustained occlusion produced a significant change in near heterophoria in 10 out of the 21 subjects examined, but no significant change in AC/A was observed in either the adapting or non-adapting subgroups. Accordingly, while the sustained output of slow fusional vergence will influence clinical measurements of heterophoria, its presence does not alter the stimulus AC/A ratio significantly.