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CASE REPORT
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
181
Case Study: Treatment of Adult-onset
Constant Esotropia with Lenses,
Optometric Vision Therapy and Prisms
Robert Lederman, BSc(Hons) Optom, FCOVD
Jerusalem, Israel
ABSTRACT
Background
There are few documented cases, and no cases
with a video journal recording a successful
outcome from non-surgical treatment of adult-
onset constant esotropia. Resolving diplopia
caused by sudden onset esotropia is typically
achieved through the application of prisms,
or surgery. Surgery can resolve the diplopia
and significantly reduce the strabismic angle,
sometimes entirely. The application of prisms can
resolve the diplopia but not alter the strabismic
angle . Optometric vision therapy as a treatment,
with or without the use of compensatory prisms,
is rarely offered.
Case Study
This paper describes the history, diagnosis,
and management of a large adult-onset con-
stant esotropia in a 27-year-old male with
anomal ous correspondence, whose microtropia
had decompensated into a large constant 40^
esotropia. This patient had been suffering with
constant diplopia for over two years. He had been
informed by several ophthalmologists that only
surgery could provide a solution. He had also
been informed by an orthoptist that orthoptic
treatment would be unsuccessful and was to be
avoided as it could result in intractable diplopia.
Together with video documentation, this paper
shows how, using lenses, prisms and optometric
vision therapy, the patient’s diplopia was resolved,
anomalous correspondence was maintained and
the esotropia was reduced to 4^. The patient’s
final situation is one in which he enjoys single
vision and excellent cosmesis without the need
for compensatory prisms.
Conclusion
This paper demonstrates that a combination
of application of lenses and prisms, together
with optometric vision therapy was effective in
providing a satisfactory subjective resolution in
the case of a 27-year-old male with a large angle
adult-onset constant esotropia. It demonstrates
that optometric vision therapy essentially provided
the opportunity for this patient to learn how to
control and sustain divergence, while effectively
avoiding potential negative consequences of
disturbing any existing sensory anomalies.
INTRODUCTION
There are few published case studies docu-
menting the treatment, either complete or
partial, of esotropia using optometric vision
therapy or orthoptics.1,2,3 In a recent prospect-
ive study of treatments for 110 adults with
divergence insufficiency-type esotropia, three
treatment types were available: surgery, prism,
or divergence exercises/therapy. The treat ment
was chosen at the investigator’s discretion.
Only 3% were prescribed divergence exercises/
therapy.4 Considering this, together with the
fact that divergence insufficiency eso tropia is
on the rise,5 there is significant import ance in
Correspondence regarding this article should be emailed to
Robert Lederman, BSc(Hons) Optom, FCOVD, at lederman66@
gmail.com.
All statements are the author’s personal opinions
and may not reflect the opinions of the College of Optometrists
in Vision Development, Vision Development & Rehabilitation
or any institu tion or organization to which the authors may
be affiliated. Permis sion to use reprints of this article must
be obtained from the editor. Copyright 2022 College of
Optometrists in Vision Development. VDR is indexed in the
Directory of Open Access Journals. Online access is available
at covd.org. https://doi.org/10.31707/VDR2022.8.3.p181.
Lederman R. Case Study: Treatment of adult-onset con-
stant esotropia with lenses, optometric vision therapy and
prisms. Vision Dev & Rehab 2022; 8(3):181-96.
Keywords: diplopia, esotropia, prism,
strabismus, vision therapy
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
182
documenting and sharing all possible ways of
resolving esotropic conditions, including opto-
metric vision therapy, so that patients and
doctors can make informed choices regard-
ing the possible treatment options. This paper
describes the history, diagnosis, and manage-
ment of a large 40^ constant esotropia with
diplopia and anomalous correspondence (AC) in
an adult male.
CASE REPORT
History
A 27-year-old male (initials: CS) attended
the author’s office for a consultation, self-
referred, after conducting an internet search
seeking a non-surgical solution to the constant
diplopia from which he had been suffering since
he was 24-years old.
CS reported that at five years of age he
experienced diplopia, and after consultation
with a pediatric ophthalmologist was diagnosed
with hyperopia, esotropia, amblyopia and
diplopia, and received glasses. Quite soon
thereafter, CS was seen by an orthoptist and
was prescribed a patching regimen of 6 days
on the left eye and 1 day on the right eye, for
most waking hours, each week for a year.
Furthermore, CS was prescribed two activities
to carry out each day when not patched. One
was an abduction activity in which CS was to
hold a fixation target in each hand, and position
it about 20cm from his face as far off to the side
as possible (one on each side, temporally). He
would then alternate his gaze from extreme
left to extreme right for a few minutes. In the
second, he would then hold the targets about
35cm apart and direct his gaze from one to the
other. No other activities were prescribed.
From age 7 years, he no longer experienced
diplopia and did not wear glasses. Age 8 years,
and now an avid reader, CS developed myopia
and the first pair of glasses he received were
-3.00D. CS reports that his Rx continued to
increase, creating a need to change his power
approximately every 2 years. With glasses, CS
felt visually comfortable when looking at far but
would typically remove his Rx for reading. He
recalled that reading was uncomfortable and
effortful when wearing his Rx.
In 2017 at age 23, CS was on vacation in
France and his glasses broke. He went to an
optometrist who issued contact lenses based
on the measurement of his previous spectacle
prescription. His prescription at that time was
OD -7.50-1.50 x 104 OS -8.25-2.00 x 80. The
lenses issued were, to the best of his memory,
OD -9.50 and OS -10.0 (fig.1)
The accurate spherical equivalent for the
contact lens based on the supplied spectacle Rx
is OD -7.50 DS and OS -8.37DS. This resulted in
CS being over-corrected by approximately 2D
in each eye. CS recalled that the optometrist
mentioned specifically that the contact lenses
issued were not the correct prescription and
were only a temporary solution until CS could
find a better one. CS wore the lenses for a few
weeks but was quite aware that reading was
difficult with them. Nevertheless, he continued
wearing them as he did not wish to purchase
new spectacles while in France.
On return to Israel, he purchased new
lenses with a different prescription (details
unavailable). Thereafter, and still feeling that
things were not quite right, CS went to an
optometrist for an examination and purchased
glasses. During the next two years, he continued
to feel that things were not optimal. One day,
while studying in classes for his matriculation
examination he arrived at class and saw “two
boards.” He recalled a very strong emotional
feeling that he “was 5 years old again.”
Since that episode, he had seen optome-
trists, ophthalmologists, and an orthoptist. He
Figure 1. Package from lens issued for OS in August 2017
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
183
had been recommended to reduce his spectacle
Rx by 1D and to consider strabismus surgery
as the only possible solution for his diplopia. He
was strongly advised against orthoptic exercises.
First Office Visit
At his initial visit at the author’s practice,
CS reported his history and chief complaint
of diplopia. The diplopia he experienced
throughout the day was described as mostly
constant and horizontal. He reported that at
times he was able to ignore the diplopic image
but not for a period long enough to provide
significant relief from the diplopia. CS was in
good health, and not taking any medication.
There was no previous history of head injury
or concussion. CS supplied the reports from
previous ophthalmological eye examinations
carried out during the preceding two years
that included a description of the esotropia as
concomitant. The records supplied included the
results of a cycloplegic refraction carried out
prior to his consultation with the author. The
findings were OD -7.00-1.50 x 100 and OS -9.00-
2.00 x 80, effectively ruling out pseudomyopia.
The most recent report was from an examination
carried out a year prior to consulting with the
author including a recommendation for an MRI,
which was negative. These findings together
with all previous examinations, ruled out any
concern regarding eye disease. Ophthalmoscopy
carried out by the author revealed well-defined
margins and healthy pallor of the optic disc.
Best corrected vision on refraction was OD 20/30
with -7.25 -1.50 x 97 and OS 20/20-1 with -8.25
-2.00 x 82. Unilateral cover testing confirmed
a constant right esotropia at far and near with
the full distance spectacle prescription in
place. Magnitude at far was approximately 40
prism diopters (^) base out (BO) and BO 45^
at near. The concomitancy of the strabismus
was confirmed. Subjective trials of BO prism
resulted in resolution of the diplopia with BO 35^
a while viewing a single character (20/50) at 6
meters, while at 35cm wearing the full distance
Rx, a prism of BO 40^ was required. With these
neutralizing prisms in place, unilateral cover
testing of the left eye revealed a small ”flick”
of the right eye temporally as it took up foveal
fixation. Additional BO prism did not neutralize
this residual small angle esotropia, which is
characteristic of anomalous correspondence.
Centration at near was evaluated using the
method described by Brock.6 While CS was
unaided, a penlight was brought to his nose
resulting in a decrease in the esotropic angle
coincident with CS report seeing the diplopic
images approach one another. At approximately
7cm from his nose he reported single vision. A
subsequent unilateral cover test of OS resulted
in a small “flick” temporally of the right eye
indicating that esotropia was still present. His
report of single vision in the presence of right
esotropia can be interpreted as suppression
of OD or anomalous correspondence. Bagolini
testing conducted at the centration point
resulted in the reporting of a perceived X with
a small gap in the crossing point of the X in
the light streak perceived by the right eye.
As mentioned, while viewing the Bagolini
‘X’, a unilateral cover test revealed a small
right esotropia. The patient perception of the
X with a small gap in the presence of small
angle right esotropia is consistent with small
central suppression coupled with harmonious
anomalous correspondence.
Fig.2.Arrangementofvectogramwiths5ckerforBrockGrossStereoAwarenessTest
Figure 2. Arrangement of vectogram with sticker for Brock
Gross Stereo Awareness Test
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
184
eyes, no activities are done which would reward
or reinforce the patient when the eyes are in the
deviated position.” Furthermore, the patient case
history and some of the findings gave reason to
be optimistic of a cure through optometric vision
therapy alone.
Treatment Plan
The treatment plan was to primarily use
peri pheral stereo targets that would provide
adequate feedback to CS regarding the state
of his peripheral sensory fusion while simul-
taneously providing the opportunity for CS to
experience proprioceptively when his eyes were
Additional unaided sensory fusion testing
resulted in positive perceived float with the
Brock Gross Stereo Awareness Test and
quoit vectogram set at “3”, in a slide holder
upon which had been placed a central sticker
(Fig.2). The float of the quoits vectogram was
maintained to 12-15 cm from CS’s nose.
Visuoscopy showed a central and steady
fixation of the left eye, and a slightly less stable
but central fixation of the right eye ruling out
steady eccentric fixation.
CS’s ability to diverge his eyes from a
fixation stick held at 5cm to quoits held at 30cm
was evaluated and unsurprisingly, CS was
unable to organize his visual posture and diverge
to meet the visual challenge of this task.
A +3.00 add reduced his near esotropia to
approximately 20^. In addition, it extended the
range of the centration point significantly. This
result prompted prescription of a progressive
addition lens (PAL) with a +3.00 addition for
general use, and a +3.00 add single vision Rx to
be worn at home as much as possible.
The author suspects that wearing contact
lenses that were over-minused by 2D was
contributory in the break down of the micro-
strabismus to a large angle constant esotropia.
Amplitude of accommodation (RAF rule)
was 10D for each eye, and monocular accommo-
dation facility was 16cpm.
CS achieved the maximum attainable score
of 5 on all aspects of a modified Northeastern
State University College of Optometry (NSUCO)
Oculomotor Test. The modification was that each
eye was tested monocularly, while the eye not
being tested was occluded with a black patch.
A summary of the initial examination find-
ings can be seen in Table 1.
A one-month follow-up was arranged to
assess the effect of the glasses with the +3.00
add. Compensatory BO prism to relieve the
diplopia was withheld per his demonstrated
degree of sensory fusion. The author under-
stood this approach to be consistent with the
philosophy of Flax7 that “since the goal of
treatment is to develop a postural set for straight
Table 1: Initial and final findings showing changes (only)
13.8.20 29.8.21
Chief
Complaint #1
Constant diplopia No diplopia
Chief
Complaint #2
Bothered by
appearance
Delighted by
appearance
Refraction OD -7.25 / -1.50 x 97
OS -8.25 /-2.00 x 82
OD -6.75/ -2.00 x 97
OS -8.00 /-1.75 x 85
Add+3.00
Distance Acuity OD 20/30 OS 20/20-1 OD 20/25+3
OS 20/20-1
Near Acuity OD 20/30 OS 20/20
Unilateral Cover
test with prism
(distance)
approx 40^ right
esotropia
4^ right esotropia
Unilateral
Cover test with
prism (near)
approx 45^ right
esotropia
4^ right esotropia
with near ADD
Full Rx: Required
prism to
resolve diplopia
(distance)
Base out 35^ Base out 4^
Full Rx: Required
prism to resolve
diplopia (near
with no Add)
Base out 40^
Motility Full
Modified NSUCO 5/5 in all aspects
Amplitude of
accommodation
10D OD and OS
Facility of
accommodation
(monocular)
16 cpm OD and OS
Central sensory
status
Anomalous
correspondence
Worth 4 dot Fusion (AC) at 7cm Fusion (AC) at 6m
Stereopsis
Titmus
400 seconds no
Rx @ 7cm
200 seconds
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
185
postured correctly. The target would provide
positive feedback i.e., fusion and “float” when
he postured his eyes correctly. CS would learn
control of his extraocular muscles so that with
time and through repeated regular practice,
he would learn to posture his eyes with greater
automaticity to achieve the desired result.
As Bruenech8 suggests, repetition increases
neurogenesis and improves the propriocep-
tive feedback from extra-ocular muscles while
simultaneously serving to attenuate neurode-
generation. In a comparable way to any learned
skill e.g., learning to play the piano, one first
carries out the task with conscious awareness,
and then as proficiency is achieved, the task
is carried out with automaticity. Expansion of
CS’s area of motor-fusion into space would be a
strong component of the treatment plan. In other
words, initially CS would experience single vision
in near space and diplopia at far. Treatment
would be directed at slowly expanding the area of
efficient seeing, from near to far.
Optometric vision therapy activities directed
specifically for removing central suppression or
treating the central AC were to be excluded from
the treatment plan. (See Discussion). Though
the Brock string was prescribed, only the
proprioceptive and visual-spatial aspects of the
activity were emphasized.
The main goal of the treatment was
the restoration of CS’s situation prior to the
decompensation of his microtropia while
leaving him with far more robust motor fusion
than he had previously enjoyed. In other words,
resolution of the diplopia, reduction of the angle
of the esotropia and the ability to maintain the
sensory situation. No part of the treatment
would be directed specifically to resolving the AC
or the monofixation syndrome.
Second Office Visit
Approximately one month later CS attended
the author’s office for the second time. As
instructed, CS was wearing the single vision
Rx at home and was feeling more comfortable.
Abduction activities were prescribed in which
CS was instructed to look from a straight-ahead
posture to as far temporally as he was able,
and to hold that posture for 2 seconds before
returning to straight ahead gaze. This exercise
was conducted for 2 minutes on each eye, twice
daily. Instructions were given that if any therapy
activity caused moderate discomfort, it should be
stopped. CS was also instructed to report to the
author if any therapy activity caused discomfort
for longer than 5 minutes after it was conducted.
Third Office Visit
At his third visit CS attended the author’s
office saying that he had spent as much
time as possible wearing the lower Rx and
that the abduction exercise had been useful.
He remarked that he felt that the near Rx
had been beneficial and reported that the
space between the diplopic images at far had
reduced. Elimination of diplopia at far while
viewing a 20/50 character was achieved with
a prism BO25^ and at near (30cm) with his NV
Rx, BO14^. CS was instructed regarding the
addition of specific activities to his daily regimen.
After first teaching the concepts of peripheral
awareness and zone of simultaneous awareness
(ZOSA),9 CS was familiarized with the BC515
variable tranaglyphs (Bernell) which presents
peripheral targets (two rings to each eye) and
peripheral suppression controls only (Fig.3).
When fusion is attained, the central ring appears
to “float” and be located ahead of the peripheral
VIDEO JOURNAL #1. This video shows the large magnitude
constant right esotropia per unilateral cover test. It was
documented at his second office visit.
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
186
target, due to the disparity caused by positioning
of the central rings on the slide.
CS was instructed to remove his Rx, to wear
the red/green glasses (with the red filter in front
of his right eye), and to hold this vectogram at a
distance in which he experienced the float of
the inner circle. He was instructed to move it
away from himself until the float was no longer
apparent. He was told to do this while being
attentive to attaining as relaxed a composure
as possible through calm breathing and
maintenance of a state of peripheral awareness.
Secondly, he was told to repeat this activity, but
as he does so, to cover and uncover his right
eye, allowing it to recover (diverge) so that he
experienced fusion again on the tranaglyph target.
Performing this activity without the spectacle
prescription provided the patient with a very
high plus addition, effectively counteracting the
accommodative aspect of the esotropia.
In addition, “whole body” abductions were
prescribed. For example, in this activity a person
with a right esotropia would fixate a target with
his right eye and turn to his left side, while
maintaining fixation on the target, as he turns.
The patient is encouraged to rotate his neck,
using its full range of motion, and of course, to
abduct maximally, with the goal of maintaining
fixation.
Fourth Office Visit
At his fourth visit, CS reported feeling strong
emotions immediately following his home vision
vergence therapy sessions. He was now engag-
Fig.3VariableTranaglyphBC515(Bernell)
Figure 3. Variable TranaglyphBC515 (Bernell)
ing in home therapy for about 30 minutes each
day. It was difficult for him to verbalize these
emotions other than to say that following the
vergence activities, he would meditate for 10
min, usually by utilizing breathing techniques.
Fifth Office Visit
Now four months after his initial consulta-
tion, CS was seen again and reported feeling
that progress was being made. However, there
was no measurable change. At this visit a simple
exercise to develop proprioceptive feedback
and awareness of what divergence feels like,
was introduced. CS was instructed to hold a
fixation stick at 5cm from his nose and then to
attempt to actively diverge his eyes towards the
tranaglyphs target set at zero, with no added
divergence demand. As success was achieved,
CS was instructed to increase the separation
of the targets, thus increasing the demand for
negative fusion.
In addition, CS was instructed regarding a
smooth vergence exercise, which required slow
separation of the tranaglyph targets, thereby
increasing the demand for negative fusion.
Sixth Office Visit
7 months after his initial examination and
after having missed an appointment one month
earlier, CS reported that he preferred doing
all prescribed vision therapy activities without
glasses, as it made the experience feel more
“natural”. While wearing his PAL’s and fixating
a distance target (20/50) his diplopia could now
be eliminated with a BO16^ prism. CS was able
to maintain a stable posture with the prism in
place. A unilateral cover test of the left (non-
strabismic) eye would elicit a small “flick”
temporally of the right eye. This is consistent
with monofixation syndrome. Fresnel prisms
were affixed to his PAL’s, OD 9^ OS 7^. CS
was familiarized with the Brock string and an
exercise was prescribed in which he had to
direct his gaze from the nearest to the furthest
bead that he could comfortably fixate. Any
instructions that would bring attention regarding
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
187
whether one or two strings were perceived in
close proximity to the bead being viewed were
purposefully avoided, in order help maintenance
of the largest ZOSA possible. CS was instructed
to look from bead to bead with a conscious
awareness of redirecting his gaze within a
volume of space, from an area close to himself
to an area further away. In other words, the
author did not want CS to experience only one
bead at a time, i.e., sequentially. On the contrary,
CS was encouraged to maintain an awareness
of the volume of space between himself and the
furthest bead, and to try and experience a willful
redirection and relocation of his gaze within that
perceived volume of space.
Seventh Office Visit
One month later, at his seventh visit CS
reported that it had taken some time to adjust
to wearing the prisms. He reported that he
had initially felt discomfort at near but that
continuous work on the Brock string had been
helpful in this regard. He could now achieve
elimination of the diplopia with an overall prism
of BO10^ (See video journal #2c). However, to
maintain comfort, the prism was reduced by
BI3^, by changing the left Fresnel prism to BO4^.
When discussing the Brock string activity,
it became apparent that CS had not fully
appreciated the steps outlined at his previous
visit. Therefore, points made at the previous
meeting were reviewed with the suggestion that
prior to moving his gaze from the near bead
to a further one, he should first prepare the
movement by thinking about the next location
within the ZOSA to which he shall be attending,
and only then execute the movement.
At this visit, time was spent allowing
CS to deepen proprioceptive awareness of
convergence and divergence and have the
satisfaction of experiencing SILO during a jump-
duction activity. (Fig.4)
Fig.4Trainingwithquoits
Figure 4. Training with quoits.
VIDEO JOURNAL #2b. This video shows the small “flick” of the
right eye when the left is occluded, and recovery of right eye
following removal of the cover.
VIDEO JOURNAL #2a. CS’s progress can be clearly ob served.
While still wearing Fresnel prisms(BO 16^) he adjusts his
vergence to achieve fusion using a prism flipper (BI3^/ BO12^)
while observing a near fixation target.
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
188
Eighth Office Visit
CS continued to exercise and attended
the office one month later. He commented that
thinking about the space between himself and
the beads on the Brock string had proven most
helpful in improving the control of his divergence
during the activity. Prism was reduced by BI2^ to
a total of BO11^. This was prescribed in Fresnel
form as OD 7^ and OS 4^.
At this visit, CS was instructed regarding
how to use the Brock string and the tranaglyphs
in different angles of gaze.
Ninth Office Visit
Approximately one month later, 10 months
after his initial visit, a total prism of BO8^ was
prescribed.
VIDEO JOURNAL #3. CS demonstrating proficiency on Brock
string without Rx.
Tenth Office Visit
CS continued to work consistently at home
and showed continued improvement that allowed
the prescription of BO6^.
VIDEO JOURNAL #4. CS shows unstable fusion with a BO7^.
BO8^ was prescribed.
VIDEO JOURNAL #5a. Evaluating minimum prism required for
comfortable fusion.
VIDEO JOURNAL #5b. Cover Test with no prisms worn.
VIDEO JOURNAL #2c. Re-assessment of minimum prism re-
quired to achieve fusion.
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
189
Eleventh Office Visit
At this visit, and now a year after his initial
consultation with the author, the prism was
reduced to a total of BO4^.
Twelfth Office Visit
The gains have been maintained. A break of
BI8^ was achieved with quoits at 35cm.
VIDEO JOURNAL #6a. Brock string with improved ranges
wearing a BO6^.
VIDEO JOURNAL #6b. Cover test wearing BO6^.
VIDEO JOURNAL #7. Cover test with no prisms worn.
Thirteenth Office Visit
Fourteenth Office Visit
Nineteen months after his initial visit, CS
attended the office just to inform the author that
he had independently removed the remaining
BO4^ Fresnel prism from his glasses, and that
he was feeling great. Though CS was unable to
see any random dot stereo targets on the Paul
Harris Stereopsis Test, testing with the Titmus
stereo test revealed that he was now able to
achieve 200 seconds contour (local) stereopsis.
This pattern of stereopsis is consistent with
monofixation syndrome.
He remarked that after intense close work,
he felt that his divergence ability was affected. CS
was reminded of the importance of good visual
hygiene (20:20:20) and of the need to ensure that
he looks sufficiently down his PAL’s to benefit
VIDEO JOURNAL #8a. Divergence at near using quoits. Achiev-
ing recovery of BI8^.
VIDEO JOURNAL #8b. Cover test showing phoria of the right
eye and “flick” when the left eye is covered.
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
190
from the full power of the reading addition.
Improper use of PAL lenses has been implicated
as a possible cause for divergence insufficiency
esotropia by Chen et al.5
VIDEO JOURNAL #9a. Observing recovery after prolonged cover
test of the right eye.
VIDEO JOURNAL #9b. Using a Mallet Unit to show that the
esophoria remains uncompensated as BO prism is added.
VIDEO JOURNAL #9c. Observing “small flick” of right eye when
left eye covered, and recovery of right eye on prolonged cover
test.
Quick Comparison
Table 1 shows findings at the initial examin-
ation, and on August 29, 2021, after which there
were no significant measurable changes. Sub-
sequent visits showed the improvement was
being maintained. On 15.3.22, CS voluntarily
removed the BO4^ prism. Following is a video
journal showing 3 stages in the treatment of
CS’s esotropia. Figure 5 illustrates the cosmetic
improvement.
VIDEO JOURNAL #9d. Seeing paradoxical physiological diplopia
with BO40^ prism.
VIDEO JOURNAL #9e. Observing smooth jump convergence
and divergence.
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
191
VIDEO 23.9.20.
VIDE O 2 5.7.21.
VIDEO 15.3.22.
Figure 5. Pre- and post-treatment images.
DISCUSSION
Re-examining the Evidence
Having observed CS’s process and facilitated
the return to his former binocular motor and
sensory status, it is worthwhile re-visiting his
childhood visual history. At his first examination
at age 5 years, after experiencing diplopia,
CS received the diagnosis of hyperopia. It
would be fair to surmise that CS had partially
accommodative esotropia in which a small
magnitude constant right esotropia remained
with the hyperopia glasses in place. If that is
true, then given the fact hyperopia diminishes
with age, why had CS not experienced diplopia
previously? The author suggests that that the
presence of a high AC\A with a school-based
increase of near-vision tasks, presented a
load beyond CS’s fusion abilities precipitating
manifest esotropia with diplopia.
CS reports that from the time he was seven,
he did not experience diplopia and from 7-8 years
he wore no glasses.
The reported occlusion treatment for ambly-
opia suggests to me that CS had a well-established
microstrabismus of the right eye, with AC. From
the age of 5 years to 8 years, CS’s Rx changed
from hyperopia to three diopters of myopia. The
author suggests that the reported resolution to
the diplopia (see History) was unrelated to the
occlusion treatment or to the activity in which CS
directed his gaze from one target to another held
35cms apart, though perhaps related somewhat
to the first exercise that demanded a full alternate
abduction of each eye. The author suggests that
it was more likely related to the development of
myopia which resulted in lessening the amount of
accommodation required by CS during sustained
tasks carried out at near. Essentially, as a
-3.00D myope who was not wearing his Rx, CS
was carrying out close work with the equivalent
of a +3.00-reading addition. What substantiates
this suggestion is the fact that CS typically
removed his Rx for reading because wearing the
prescribed Rx was challenging his fusion when
carrying out near-vision tasks.
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
192
Clinical Insights
Video Journal 1: This video shows clearly that
CS’s esotropia was not the result of a complete
inability to direct his eye to straight ahead gaze.
A weak lateral rectus eye muscle is not the
cause of this esotropia. The author suggests that
it is not the cause of most esotropias though it
is imperative to completely rule out neurological
issues, as had been done in this case.
Video Journal 2a: This video shows how CS
can demonstrate positive and negative fusion.
He is posturing his gaze nearer and further. One
can observe how he is computing the situation
and responding appropriately. One can see that
he has already learned to diverge, and that even
though he has esotropia, convergence is not
simple either. The prism causes slight diplopia
and CS’s visual system responds to resolve
the diplopia that the prism is causing. Even in
this short clip one can observe how repetition
improves his ability to reorganize his gaze more
rapidly. He is learning what motor response to
make to create a desired visual percept.
Video Journal 2b: This video shows the
“flick” consistent with monofixation syndrome.10
Sometimes the terms monofixation syndrome
and microstrabismus are used interchangeably.
Observing to see if there is a “flick” in the
presence of neutralizing prisms reveals that
the situation prior to the decompensation of the
microstrabismus was monofixation syndrome.
This is an important point because it shows that
the presence of a large angle strabismus should
not prevent the clinician from attempting to
identify the presence of monofixation syndrome,
which can be mimicked in the presence of
neutralizing prisms. Confirmation of monofixation
syndrome supports the suggestion that this was
a long-standing situation that decompensated.
Note that the dissociated deviation is greater
than the associated deviation, which is one of the
signs of monofixation syndrome. Sensitivity to the
patient’s comfort is essential to maintain positive
progress throughout the treatment. If the patient
feels stressful because they are on the verge of
becoming diplopic, things can go awry. If a patient
loses confidence in the treatment process, or
trust in their therapist wavers consequently to
experiencing visual stress, it can jeopardize a
potentially successful outcome. Giving sufficient
prismatic support is therefore advisable.
Video Journal 6a: This video shows the
use of the Brock string to develop more effi-
cient independent control of divergence and
convergence, nurturing the ability to explore
space more effectively. This exercise also
facilitates further reduction in the power of the
compensatory prism required.
Video Journal 8a: This video demonstrates
the existence of peripheral sensory fusion
and depth perception despite the presence of
a microstrabismus. Patients with strabismus
will typically report having been told by eyecare
professionals, that they have no appreciation of
depth. But patients even with moderate angles
of strabismus can fuse peripherally using large
targets and appreciate depth perception.
Video Journal 9b: In this video one can see
that in the presence of a microstrabismus, the
polarized nonius lines of the Mallett distance
fixation disparity unit are perceived without
suppression and demonstrate fixation disparity,
with eso-slip of the right eye. CS’s response
in this test shows that though he suppresses
foveally, he can respond binocularly just a few
degrees out into peripheral retina. This is typical
of monofixation syndrome.
Uniqueness of This Case Study
This case study is unique because it provides
a video journal that records the improvement
without surgery, in a person with an adult-onset
constant large angle esotropia with diplopia
and AC. Crouch et al.4 report that “possible
allocation bias” might be a factor in the fact that
only 3% of subjects in their study were offered
divergence exercises/therapy, even though 58%
of the participants had an esotropia angle at far
of less than 15^, with a strabismic angle at least
25% smaller measured at near. This study may
therefore encourage professionals to consider
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
193
offering optometric vision therapy in combination
with prism application as an option for treatment.
It is important to point out that CS is a highly
motivated, intelligent young man; a model
patient. Typically, the author insists that patients
attend weekly in-office therapy sessions. How-
ever, this was deemed unnecessary in this case.
In retrospect, the author concludes that prisms
prescribed earlier on in the treatment as others1
have described, may have accelerated the
treatment. Table 2 shows how approximately five
months after the initial prescribing of prism, maxi -
mum improvement had already been attained.
Though the prognosis that the eyes in a
patient with monofixation will remain unchanged
throughout life is excellent,11 this was certainly
not the case in this instance. His prior situation
had decompensated, supposedly related to his
high AC/A and the wearing of an over-minused
Rx. This is a potential situation described by
Lang.12 Bringing a visual system back to familiar
sensory-motor territory is quite different to
attempting to charter new sensory-motor ground.
(For a personal account see Fixing My Gaze).13 In
fact, in this case, the sensory situation remained
essentially unchanged. This consideration is of
critical importance when considering treatment
options for many adults (whose new-onset
divergence insufficiency represents 10% of all
new-onset adult strabismus),14 as they too have
Table 2: Prism required for fusion and prescribed prism
Date of
Visit
Visit # Prism Required
for Fusion (DV)
Tot al P r i sm
prescribed
RE LE
13.8.20 1 35^
23.9.20 2 35^
25.10.20 3 25^
25.11.20 4 25^
20.12.20 5 25^
24.1.21 No
Show
14.3.21 6 16^ 16^ 9^ 7^
18.4.21 7 10^ 13^ 9^ 4^
19.5.21 8 10^ 11^ 7^ 4^
21.6.21 9 7^ unstable 8^ 8^
25.7.21 10 6^ 6^ 6^
29.8.21 11 4^ 4^ 4^
a well-established sensory-motor landscape. In
fact, the positive treatment outcomes reported by
Crouch et al.4 due to application of prisms (62%
at 12 months) or surgery (79% at 12 months)
attest to this fact. Without an established sensory
landscape, there is no “cement” to maintain the
motor fusion. But due to lack of documentation, it
is less well known that optometric vision therapy
can be remarkably effective in these cases.
Nevertheless, treating people with esotropia
is never simple, and sufficient experience and
knowl edge in optometric vision therapy is essen-
tial before attempting to treat these cases.
One is also able to see how the optometric
vision therapy treatment improved the patient’s
ability to regain fusion by enhancement of the
quality of the proprioceptive feedback from the
extra-ocular muscles. Moreover, it was the
combined use of optometric vision therapy and
prisms that allowed for gradual reduction of the
strength of the compensatory prism required
for fusion. In other words, as each successively
weaker prism was prescribed, CS was able to use
optometric vision therapy activities to extend his
locus of fusion from peri- to extrapersonal and
yet further still, into distant space. This resulted
in yet further reduction of the strength of the
required compensatory prism. This improvement
can be readily seen when comparing Video
Journal 5b with 9c. The overall change in CS’s
ability to control his eye gives clinical support
to the ideas expressed by Dr Jan R. Bruenech15
that “if you stimulate the oculomotor system…
you can enhance the function of the receptor
(myotendinous cylinder) itself…and you will
enhance the oculomotor system’s ability to
compensate for heterophorias.”
SUMMARY
This case demonstrates clearly through a
video journal, the possibility of treating adult-
onset esotropia with AC using a combination of
lenses, optometric vision therapy and prisms.
It shows that in this case, binocular sensory
fusion was present simultaneously with mono-
fix ation syndrome and AC. In fact, Parks16
Vision Development & Rehabilitation Volume 8, Issue 3 • September 2022
194
describes the characteristics of monofixation
syndrome as always having “vergence ampli-
tudes and stereopsis”, and sometimes having “a
strabi s mus history, anisometropia, a unilateral
macu lar lesion, amblyopia, eccentric fixation,
orthophoria, phoria, small tropia, and possibly
a deviation that is larger by alternate cover than
by cover-uncover.” It documents that in this
case it was possible to train divergence and
wean the patient off compensatory prism, as
well as avoid the need for surgery.
This case shows that as long as no attempt
is made to actively eliminate central suppression,
peripheral fusion is stressed and the “flick” on the
unilateral cover test is allowed to remain, doctors
with fear of intractable diplopia should not be so
cautious that they deprive patients of non-surgical
solutions to esotropia, if that is what they seek.
Moreover, it emphasizes the need to approach
such cases only after one is thoroughly familiar
with the sensory-motor and perceptual aspects
of strabismus and strabismic seeing. This will
enable the practitioner to adopt the appropriate
and most effective strategies for each case.
This case is consistent with Caloroso’s17 ob-
serv ation that “though moderate- to large-angle
esotropes have poor cosmesis and to the novice
may appear to be the most difficult to treat,
it is frequently the constant micro or small-
angle esotrope who is the least responsive to
treatment.”
Where the only option offered by the optom e-
trists, orthoptist and a number of ophthalmolo-
gists was surgery, it was optometric vision
therapy combined with lenses and prisms that
produced a satisfactory outcome for this patient.
This was not an option that was available as a
treatment choice in the study by Crouch et al.4
While surgery may have produced a satis-
factory outcome, the patient was looking for
a non-surgical resolution of his condition and
found it.
One of the purposes of the study by Crouch et
al.4 was “to determine the frequency of specific
treatments across a large group of eyecare
providers.” The video-documentation provided
in this case study should encourage more
eyecare professionals to consider optometric
vision therapy, possibly combined with lenses
and prism application, as a treatment option for
patients with adult-onset esotropia and diplopia.
REFERENCES
1. Baxstrom CR. Nonsurgical treatment for esotropia
second ary to Arnold-Chiari I malformation: A case report.
Optometry-Journal of the American Optometric Association.
2009 Sep 1;80(9):472-8. https://doi.org/cgxp6v
2. Budd A. Reverse exercises in a case of intractable
diplopia. Strabismus. 2021 Apr 3;29(2):116-9. https://bit.
ly/3Drpm4r
3. Lee Y, Park CW, Kim H. A Case Report of Successful
Vision Therapy in Divergence Insufficiency Esotropia.
대한시과학회지. 2020 Sep 30;22(3):295-303. https://doi.
org/jbtm
4. Kraus CL, Gunton KB, Repka MX, Marsh JD, Del Monte
MA, Luke PA, Peragallo JH. A prospective study of
treatments for adult-onset divergence insufficiency–type
esotropia. Journal of American Association for Pediatric
Ophthalmology and Strabismus. 2021 Aug 1;25(4):203-e1.
https://doi.org/jbtn
5. Chen X, Marsh JD, Zafar S, Gerber EE, Guyton DL.
Increasing incidence and risk factors for divergence
insufficiency esotropia. Journal of American Association
for Pediatric Ophthalmology and Strabismus. 2021 Oct
1;25(5):278-e1. https://doi.org/jbtp
6. Brock FW. Visual Analysis for Strabismus or Strabismic
Tendencies. New York Optometric Foundation 1949, Lec-
tures. 1-2
7. Flax N. Management of Divergence Excess Intermittent
Exotropia J Behav Optom 1996:7 (3):66, 72-3 https://bit.
ly/3Leew3D
8. Bruenech JR. Neuroanatomical Structures in Extraocular
Muscles and Their Potential Implication in the Manage-
ment of Strabismus. Advances in Ophthalmology and
Optometry. 2021 Aug 1;6:39-53. https://doi.org/gkds8g
9. Cook D. The Shape of the Sky/ Optometric Extension
Program Foundation, 2019:46-50
10. Parks M. The monofixation syndrome. Transactions of the
American Ophthalmological Society. 1969;67:609. https://
bit.ly/3QnfICA
11. Parks M. The monofixation syndrome. Transactions of the
American Ophthalmological Society. 1969;67:654. https://
bit.ly/3QnfICA
12. Evaluation in small angle strabismus or microtropia,
Strabismus Symposium, Giessen, August 1966, Basel/
New York: Karger, 1968, pp. 219-22.
13. Barry SR. Fixing my gaze: A scientist’s journey into seeing
in three dimensions. Basic Books; 2009 May 26.
14. Goseki T, Suh SY, Robbins L, Pineles SL, Velez FG, Demer
JL. Prevalence of sagging eye syndrome in adults with
binocular diplopia. American journal of ophthalmology.
2020 Jan 1;209:55-61. https://bit.ly/3eA7hGR
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15. Vivid Vision. Dr. Bruenech on sensory receptors in strabis-
mics[Video] 2021 https://youtu.be/-aKEjjf0Ua4
16. Parks M. The monofixation syndrome. Transactions of the
American Ophthalmological Society. 1969;67:615. https://
bit.ly/3QnfICA
17. Caloroso EE, Rouse MW, Cotter SA. Clinical management
of strabismus. Butterworth-Heinemann Medical; 1993.
p251
PERSONAL REFLECTIONS AND
ACKNOWLEDGEMENTS
In a certain sense, this paper represents
a culmination of my work as a developmental
optometrist, certainly regarding my years of
study and treatment of strabismus. My desire to
become an optometrist was the direct result of
an eye examination I had when I was 16 years
old at the office of Jonathan Shapiro BSc(Hons)
FCOptom, FAAO, FEAOO. My excitement about
binocular vision was nurtured while studying
Optometry and Visual Science at the City
University, by Prof. Ronald F.J. Mallett FCOptom,
DOrth, and Dr. Howard Solomons, Ph.D.,
FCOptom. It was under their tutelage that my
interest in orthoptics grew, and my knowledge
expanded until I was privileged to be treating
patients in orthoptics at the world-famous
London Refraction Hospital, London, England,
which later became the Institute of Optometry.
In 1995 (now in Israel) a lady walked into my
office enquiring whether I would allow an O.D. by
the name of Leon Reich who was visiting from
the US, to examine her son who had exotropia.
She said that this doctor was able to straighten
eyes without surgery. I agreed.
The patient arrived early, and I observed
that he had a large angle exotropia. Of course,
I “knew” that the suggestion that anything but
surgery could help this child, was preposterous.
When he arrived to examine the patient, Dr. Reich
immediately asked me if I had a stick and a straw.
Well, of course I didn’t. He was flabbergasted
and proceeded to take apart my ballpoint pen
and create a “stick and straw.” Unfortunately,
in this case the patient’s attempt to visually
localize the straw being held by the doctor prior
to placing the stick into its opening, did not elicit
the desired response of convergence. But for
me it didn’t matter. My curiosity about what was
happening on the other side of the pond had been
sparked. A short while later, I joined OEP and
COVD and that was the beginning of my journey
into the world beyond classical orthoptics into
developmental optometry and optometric vision
therapy. It has been truly wonderful.
I would like to acknowledge and thank the
following friends and colleagues who have con-
trib uted significantly to my growth and ability to
treat successfully, people with strabismus. It has
been a pleasurable privilege to learn from them,
and to be inspired and empowered by them.
Dr. David L. Cook OD, FAAO, FCOVD
Dr. Robert Sanet OD, FCOVD
Dr. Samantha Slotnick, OD, FAAO, FCOVD
Dr. Curtis R. Baxstrom, MA, OD, FCOVD
Prof. Susan R. Barry, PhD
And those who have passed and from whose
texts I have gained considerably
Dr. Fred Brock, OD
Dr. Izzy Greenwald, OD, FCOVD
Dr. Don Getz, OD, FCOVD
In addition, I would like to thank Prof. Ken
Ciuffreda OD, PhD, Prof. Susan R. Barry, PhD,
and the journal reviewers for reviewing my
manu script and for their erudite comments.
Finally, I would like to thank my patient CS for
his willingness to share his own case so fully, in
this journal.
AUTHOR BIOGRAPHY:
Robert Lederman, BSc(Hons) Optom,
FCOVD
Jerusalem, Israel
Robert Lederman is in private practice in
Jerusalem, Israel, and is an acclaimed
national and international lecturer.
He graduated with Honours from The
City University (London) department of
Optometry and Visual Science (1987). In
2001 he became Israel’s first optometrist to achieve Fellowship
status from the College of Optometrists in Vision Development.
He is currently President of COVD Israel.
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CALL FOR ABSTRACTS
52nd AnnuAl meeting • April 25-29, 2023
My Approach To…
Fellow members of COVD, share your unique
approach with COVD Family from around the world!
We are excited to continue the success of the My Approach To
program, a rapid-fire lecture format that will give four COVD
Fellows the opportunity to share interesting cases and engage
with colleagues.
Individuals chosen to be presenters will receive
compli mentary registration for all education Wednesday
through Saturday for the COVD 2023 Annual Meeting!
Each presentation will be approximately 20 minutes in length,
leaving an additional 5 minutes for questions and audience
collaboration.
GUIDELINES
• 500-word abstract
• Brief history of the chief complaint
• Significant clinical findings
• Relevant test results
• Treatment protocol
• Treatment outcome
X Do not include tables, references, or slides
Email all abstracts to
meetings@covd.org by
October 24, 2022.
College of Optometrists in Vision Development covd2023.com
This event is underwritten by unrestricted funding from
SUBMIT YOUR ABSTRACT
