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226 Theory and Practice of Squint and Orthoptics
• Put on the prism glasses with the prescribed
prism power.
• Focus on a near target (e.g. a small object or
text) while wearing the glasses.
• The prisms will create a slight separation
between the images seen by each eye, which
forces the eyes to work together to maintain
single vision.
• Perform various near tasks while wearing the
prism glasses, such as reading or drawing.
4. Pencil/pen push-ups
Similar to the exercise for convergence
insufficiency, this exercise helps train the eyes
to converge effectively.
• Hold a pencil or pen vertically at arm's length,
with the tip at your eye level.
• Focus on the tip of the pencil.
• Slowly bring the pencil closer to the tip of your
nose while maintaining clear and single
vision.
• Stop if you experience double vision and then
return the pencil to arm's length.
• Perform this exercise for about 10–15
repetitions, several times a day.
Fig. 9.2 Physiologic diplopia exercises using stereogram
in the crossed position.
e. Exercises using Remy separator. For details
see page 151.
f. Reading bar exercises. For details see page 151.
Orthoptic exercises for esophoria should be
carried out weekly in the clinic and should be
supported by home exercises as discussed
above. It is important to ensure that constant
efforts to relax convergence have not resulted
in an inability to obtain a normal near point of
convergence. This should be checked at regular
intervals.
3. Base-out prism exercises
Base-out prism exercises are designed to train
the eyes to converge properly when focusing on
a near object. These exercises typically involve
using prism glasses or reading glasses with
prism lenses.
5. Brock string exercise
The Brock string is a tool that can help improve
convergence abilities and depth perception.
• Attach a colored string (around 3–4 feet long)
to a stationary object at eye level.
• Hold the other end of the string to your nose.
• Focus on the string, and you should see a
series of colored beads along the string.
• As you focus on the string, the beads should
appear to merge into a single bead, indicating
that your eyes are converging properly.
• Gradually move the end of the string closer
to your nose and repeat the process.
6. Near-far pencil exercise
This exercise helps to strengthen convergence
skills and improve eye coordination.
• Hold a pencil or pen vertically at arm's length,
with the tip at your eye level.
• Focus on the tip of the pencil.
• Alternate your focus between the tip of the
pencil and a distant object in the background.
Heterophoria
227
• Keep switching your focus between the near
and far objects while maintaining single
vision.
Consistency is essential when performing
these exercises. Your eye care professional will
determine the appropriate exercise regimen and
monitor your progress. If you experience any
discomfort or worsening of symptoms during
the exercises, consult your eye care provider for
guidance. They may also recommend additional
therapies or treatments, depending on the
severity of your esophoria.
Computer-based exercises for esophoria
Computer-based exercises for esophoria can be
a helpful addition to traditional orthoptic
therapy. These exercises are designed to
improve eye coordination and alignment. Here
are some computer-based exercises and tools
that may be beneficial for esophoria:
i. Interactive vision therapy software: Some
vision therapy software programs offer
exercises specifically aimed at improving eye
alignment and coordination. These programs
may involve tracking moving objects or
engaging with visual stimuli that challenge
your eye muscles to work together correctly.
ii. 3D and virtual reality (VR) exercises: Three-
dimensional and VR exercises can create a
more immersive and engaging experience for
esophoria treatment. These exercises
typically involve interacting with 3D objects
or virtual environments, which can help
improve depth perception and encourage
proper eye alignment.
iii. Online vision therapy platforms: Some
online platforms offer comprehensive vision
therapy programs, which may include
computer-based exercises tailored to your
specific needs. These programs are usually
supervised by eye care professionals and can
be performed at home with regular checkins.
iv. Interactive games: There are video games
and apps designed to improve eye
coordination and convergence skills. These
games often involve tasks like tracking
moving objects or completing visual puzzles
that require precise eye movements.
v. Computer-based prism therapy: Similar to
traditional prism exercises, computer-based
prism therapy uses special software to
introduce prism effects, which can help train
your eyes to converge properly while
focusing on near objects.
Note: It is more difficult to improve relative
negative convergence than relative positive
convergence. Therefore, esophorias respond less
well to orthoptic treatment alone.
Orthoptic exercises for exophoria
The aim is to improve the fusional convergence
(relative positive convergence). This can be
accomplished by the following:
a. Convergence exercise with prisms. It is similar
to that described for esophoria, except that in it,
prisms are placed base-out in front of the eyes.
While the patient is performing this exercise, the
orthoptist should watch the patient's eyes to make
certain that he/she is converging and has not
diverged and suppressed.
b. Convergence exercise using synoptophore. It
is performed as described for esophoria, except
that in it, the instrument arms are slowly
converged, beginning at an angle at which patient
can fuse the picture.
c. Physiologic diplopia exercise using
stereogram in the uncrossed position. To
perform this exercise, the stereogram card is
held at arm's length in front of the patient and a
pencil (fixation point) is placed midway
between his/her eyes and the card. When he/
she looks at the pencil, he/she will notice
diplopia (uncrossed) of the card and will see four
instead of two pictures. Patient is trained to
adjust the position of the pencil in such a way
that the two central pictures are joined into one
so that now he/she sees three pictures (Fig. 9.3).
The patient is trained to see the fused central
picture clearly. In doing so, he/she is converging
for the fixation object and accommodating for
the distance of the card, i.e. he/she is converging
relatively more than he/she is accommodating.
Patient can practise this exercise at home for a
few minutes several times a day.
d. Convergence exercise using diploscope. See
page 149.
e. Exercises for improving near point of
convergence. These are as follows:
228 Theory and Practice of Squint and Orthoptics
Fig. 9.3 Physiologic diplopia excercises using stereogram
in the uncrossed position.
i. Advancement exercise. It is a good convergence
exercise which can be done at near. In it, patient
is asked to hold a target (preferably a small
detailed picture or fine print) away from his/her
nose where fusion is possible. He/She is asked
to slowly advance the target towards his/her
nose until diplopia is appreciated. At this point,
he/she is asked to stop and try to converge more
and, thus to unite the two images again. If he/
she cannot do this, he/she should move the target
back to a small distance to get single vision and
then try to bring it closer again. This should be
repeated until the patient can converge to his/
her nose or at least reasonably close to it.
ii. Jump convergence exercise. Jump
convergence is more elaborate and more
effective form of the 'picture-to-nose'
convergence exercise. It trains the patient to
achieve bifoveal single vision following a
sudden change in the convergence requirement.
This is usually possible only after convergence
has been improved to some extent by other
exercises and therefore, is not used before the
fourth week of convergence training,
depending upon the progress. This exercise may
be carried out by any of the following methods:
• Alternate fixation on distance and near target. The
simplest way of doing this exercise is to have
two fixation targets, one fixed target at a
distance of about 6 metres and other movable
target held about 33 cm in front of the eyes.
The patient is asked to change his/her fixation
repeatedly between the distance and near
targets. Subsequently, the near target is
brought closer to the eyes until he/she can
eventually change from distant fixation to
fixation at 5 cm while keeping one image of
the near object, even though it may be very
blurred.
• Jump convergence exercise with use of prism.
Patient is asked to fixate an object and a 10D
prism is placed base-out in front of one eye.
Patient is instructed to try to maintain single
vision. In doing so, he/she has to converge
his/her eyes. The prism is then removed and
convergence is relaxed for a few seconds. This
is repeated several times with prisms of
increasing strength until eventually the
patient can converge to overcome a 40D
prism.
• Jump convergence exercise with synoptophore.
Patient is asked to join the two pictures from
stereopsis slides. He/she is then asked to look
up on a distant target, while the orthoptist
moves the tubes of instrument into slightly
more convergent position. Patient is then
asked to look back at the pictures. Patient will
have to converge to obtain single vision. This
is repeated several times, converging the
instrument tubes more each time, until the
patient can converge to overcome an angle of
60D.
3. Role of miotic drugs in
the treatment of heterophoria
Miotic drugs are the treatment of choice in near
esophoria due to a high AC/A ratio. Miotics
facilitate accommodation, so that less than
Heterophoria
229
normal innervation is necessary to obtain a
given accommodative response and consequently there occurs less accommodative
convergence. Therefore, miotics are useful aid
to orthoptic treatment in convergence excess
type of decompensating esophorias, if orthoptic
treatment alone is insufficient to relieve the
symptoms.
Miotics do not affect the distance deviation,
for distance vision, no accommodation is
necessary, if full correction is provided by
glasses. However, if for some reasons, full
optical correction has not been provided, the
distance esophoria will also show a decrease.
Usually, phospholine iodide 0.06%, or 0.125%
is used once daily.
4. Role of prisms
• Prisms may be used as a training device for
orthoptic exercises as discussed above. They
may also be incorporated as a permanent
correction in the patient's glasses, or they may
be clipped on by the patient for specific
purposes only.
• Role of prisms as a permanent correction in
horizontal phorias is debatable. They should
be considered only after other measures have
failed to relieve the symptoms. For
exophoria, base-in prisms and for esophoria
base-out prisms are incorporated into the
glasses.
• Primarily, prisms are prescribed as a
permanent correction in the treatment of
comitant vertical phorias. A vertical prismatic
correction of 10D is the maximum amount
that can be tolerated. There is no fixed rule as
to the amount of prism correction to be given
in a particular patient. However, in practice,
prism is prescribed with apex towards the
phoria to correct only half or at the most twothirds of total heterophorias.
5. Surgical treatment of heterophoria
Indications
• Horizontal phorias. Surgery becomes necessary
only when symptoms cannot be relieved by
other methods. This is most frequently true,
when the basic deviation is too large to be
controlled despite good fusional vergence. An
operation is also indicated in phorias of
anatomic or paretic origin for which other
treatment methods cannot be successful.
• Vertical phorias. In many hyperphorias,
especially those of paretic origin and those too
large to be corrected by prisms, surgery is the
best treatment.
• Cyclophorias. Surgery is the only treatment of
cyclophorias.
Amount of surgery
It is an erroneous attitude to think that lesser
amount of surgery is required in heterophorias in
comparison to heterotropias. In fact, the amount
of surgery must be aimed at the basic deviation
and the goal to align the eyes, regardless of
whether it is a latent, intermittent or manifest
deviation. However, a conservative approach has
been recommended when considering surgery in
patients beyond 50 years of age.
BIBLIOGRAPHY
1. Crone RA: A new theory about heterophoria.
Ophthalmologica 1971;162:199.
2. Flynn JT, Grundmann S, Mashikian M:
Binocular suppression of scotoma: its role in
phorias and intermittent tropias. Am Orthopt J
1970;20:54.
3. Jampolsky A, Flom B, Fried A: Fixation disparity
in relation to heterophoria. Am J Ophthalmol
1957;43:97.
4. Palmer EA, Noorden GK von: The relationship
between fixation disparity and heterophoria.
Am J Ophthalmol 1978;86:172.
5. Scobee RG: The oculorotary muscles, 2nd ed.,
St. Louis. 1952, Mosby-Year Book, Inc.
230 Theory and Practice of Squint and Orthoptics
10
Concomitant
Esotropias and Exotropias
CONCOMITANT ESOTROPIAS
Definition
•
Classification
•
Infantile esotropia
•
Accommodative esotropias
•
– Refractive
– Nonrefractive
– Hypoaccommodative
– Partial accommodative
Acquired non-accommodative esotropias
•
Sensory esotropia
•
Consecutive esotropia
•
CONCOMITANT ESOTROPIAS
DEFINITION
Concomitant esotropia is the term used to
describe any manifest convergent deviation of
the visual axes in which the amount of deviation in the squinting eye remains constant
(unaltered) in all the directions of gaze and
there is no associated limitation of ocular
movements.
In general, development of an esodeviation
has got three stages:
1. Stage of latent esodeviation. In this stage, the
esodeviation is kept latent by the control of
fusional divergence reserve. It is also called the
stage of esophoria. It has been described in detail
on page 220.
2. Stage of intermittent esodeviation. In this
stage, the fusional divergence reserves which
usually keep the deviation latent, become
inadequate intermittently resulting in intermittent manifest esodeviation (intermittent
esotropia).
CONCOMITANT EXOTROPIAS
Congenital (infantile) exotropia
•
Primary exotropia
•
– Etiology
– Classification
– Intermittent exotropia
– Constant exotropia
Sensory exotropia
•
Consecutive exotropia
•
3. Stage of constant esodeviation. When the fusional
divergence amplitude becomes inadequate to
maintain the latency of deviation, a permanent
manifest esodeviation, i.e. constant esotropia occurs.
Constant esotropia may be unilateral esotropia or
alternating esotropia.
Note. Since the fusional divergence mechanism
is much weaker (amplitude 4 to 6 PD) than
fusional convergence (amplitude >30 PD), the
esodeviations usually become constant with
poor stereoacuity. While in contrast, exodeviations tend to remain intermittent with good
stereoacuity for a longer period.
CLASSIFICATION
Concomitant esodeviations can be classified into
following clinico-etiological groups:
1. Infantile (congenital) esotropia. It is a large
angle esotropia that is constantly manifest and
occurs during first few months of life.
2. Accommodative esotropia. The deviation
increases, when accommodation is exerted. It
may be:
Concomitant Esotropias and Exotropias
231
i. Refractive accommodative esotropia
ii. Non-refractive accommodative esotropia
– Hyperaccommodative (high AC/A ratio)
iii. Hypoaccommodative (weak accommodation)
iv. Mixed or partially accommodative esotropia.
3. Acquired non-accommodative esotropia. The
acquired esotropia, in which deviations not
affected by the state of accommodation,
includes:
i. Essential acquired or late onset non-accommodative esotropia, which can be:
• Basic esotropia
• Convergence excess esotropia
• Divergence insufficiency esotropia
ii. Acute concomitant esotropia
iii. Microtropia
iv. Nystagmus blockage syndrome
v. Cyclic esotropia
vi. Divergence pareses
vii. Stress-induced esotropia
viii.Esotropia in myopia
ix. Esotropia due to spasm of near reflex.
4. Sensory esotropia. It results from a poor
vision in one eye.
5. Consecutive esotropia. It results following
surgical over correction of exotropia.
Unilateral versus alternating esotropia
Primary constant esotropia of any type may be
either unilateral or alternating depending upon
the type of fixation. Some of the important points
worth mentioning about each type are given
below.
Unilateral esotropia
• It occurs more frequently than alternating
esotropia.
• In it, one eye is habitually preferred for
fixation and the other eye is always deviated.
• If an anisometropia exists, almost invariably
the eye with the lesser spherical or astigmatic
error will be fixating eye.
• In patients with small angle esotropia (up to
about 15), harmonious anomalous retinal
correspondence and moderate degree of
amblyopia are found more frequently than in
those with larger deviations, in whom
profound amblyopia and normal retinal
correspondence prevail.
Alternating esotropia
• In alternating esotropia, either eye is used
alternately for fixation while the other one
assumes the deviated position.
• The patients frequently use cross-fixation,
especially when the angle of deviation is large.
• Visual acuity is almost equal in both eyes.
• Sensory adaptations in alternating esotropia
are such that while one eye fixates, the
deviating eye is either suppressed or
participates through anomalous retinal
correspondence (ARC) in binocular vision.
Incidence of ARC is high and is found with
greater frequency in patients with small angle
deviations than in those with large angles in
whom NRC prevails.
• Since either eye is used for fixation part of the
time, there is no amblyopia.
INFANTILE ESOTROPIA
Infantile esotropia (old name—congenital
esotropia) is a distinct clinical form of esotropia
which usually presents at 1–2 months of age.
However, it may be detected shortly after birth
or any time within the first 6 months of life.
Previously, it was known as 'congenital
esotropia'.
ETIOLOGY
The exact etiology of infantile esotropia is
obscure. Following factors have been implicated:
1. Innervational disturbance in the form of an
imbalance between tonic convergence and
divergence is being considered the probable
cause rather than the anatomic cause. This
view has been derived from the observation
that many a time, the eyes of such a patient
become straight or even divergent under
anaesthesia.
2. Role of accommodation. It has also been
reported that an accommodative element may
be responsible partially or wholly in some cases
of infantile esotropia. Further, in some cases, an
accommodative element may be superadded
over the basic deviation at the age of 2–3 years.
232 Theory and Practice of Squint and Orthoptics
3. General and environmental factors include
low birth weight, prematurity, perinatal
hypoxia, maternal-smoking, drugs and alcohol
abuse.
CLINICAL FEATURES
1. Time of onset. In most of the cases, squint
manifests within first 6 months of birth in an
otherwise normal infant.
2. Angle of deviation. Most patients with
infantile esotropia (Fig. 10.1) have a large angle
Fig. 10.1 A child with infantile esotropia.
of deviation for both distance and near fixation.
In half of the patients, the deviation measures
30° or more. The angle of deviation is usually
stable except in a few cases having an
accommodative element in the etiology.
3. Fixation pattern. Usually an alternate fixation
occurs in primary gaze and crossed fixation in
lateral gaze, i.e. the infant fixates the objects in the
left field with right eye and the objects in the right
field with the left eye (Fig. 10.2).
4. Apparent limitation of abduction. The cross-
fixation makes the abduction of either eye
unnecessary and thus on initial examination, the
impression of bilateral sixth nerve palsy may be
given. However, following examination techniques
may help in demonstrating the presence of
abduction:
a. Doll's head phenomenon test. This is simple,
easy and best method of demonstrating presence
of abduction in an infant. In this technique, the
examiner grasps the top of the infant's head and
quickly turns it in horizontal direction. During
this manoeuvre, an observation for the
occurrence of abduction is made in the eye
opposite to head turn, i.e. when head is
suddenly turned towards the right, the
observation should be made in left eye and vice
versa.
b. Rotating the child for demonstrating abduction.
In this technique, the examiner holds the infant
in his hands and rotates him completely first in
one direction and then the other. While rotating
towards his right the examiner should look for
a quick abductive movement in the infant's right
eye and vice versa (Fig. 10.3).
c. Alternate patching. If the above described two
techniques fail to demonstrate abduction, then
an alternate patching of the either eye should
be done for several hours. If there is no lateral
rectus palsy in the unpatched eye, the ability to
abduct will become apparent (Fig. 10.4).
5. Visual acuity is normal and equal in both
eyes of patients who freely alternate fixation. If,
however, one eye is preferred, amblyopia will
develop in the other eye.
6. Refractive errors. The refractive errors are not
prominent, but are consistent with the patient's
age group.
Fig. 10.2 Diagrammatic depiction of cross-fixation in a patient with infantile esotropia.
Fig. 10.3 Rotation of an infant to determine lateral rectus
palsy (for explanation see text).
Associations
Infantile esotropia is frequently associated with
other ocular abnormalities. Under such
circumstances, the condition is labelled as
infantile esotropia syndrome. Components
other than esotropia of this syndrome are as
follows:
1. Inferior oblique overaction. A marked degree
of overaction of one or both inferior oblique
Concomitant Esotropias and Exotropias
233
muscles may be seen in about 50–60% of patients
above one year of age. Before this age, it is rarely
seen suggesting that probably it represents an
evolutionary stage in the development of
infantile esotropia syndrome.
2. Dissociated vertical deviation (DVD). It is an
important component of the syndrome, seen in
about 70 to 90% of cases. For details of DVD,
see page 277.
3. Latent nystagmus. A jerk type of latent
nystagmus having a decreasing exponential
slow phase is another component of the
syndrome seen in about 33% cases. The
nystagmus occurs in both eyes, on occluding one
eye, with the fast component directed towards
the fixating (uncovered) eye. In patients having
alternate squint, nystagmus may occur while
both eyes are open, with a fast component
directed towards the fixating eye. Under these
circumstances, it might be confused with the
true congenital nystagmus and thus electrooculography may be indicated for differentiation.
4. Lack of bifixation. Inherent lack of capacity
for bifixation is another component of the
syndrome. Therefore, many patients with
infantile esotropia syndrome, even after full
surgical correction performed in time, do not
achieve normal stereopsis. This is one of the
causes of monofixation syndrome which has been
described on page 248.
Fig. 10.4 Patch test to detect ability of abduction in an infant: (A) momentary occlusion of the fixing eye may not suffice
to force the fellow eye to take up fixation; (B) patching for several hours may be required to detect abduction ability in the
originally non-fixing eyes.
234 Theory and Practice of Squint and Orthoptics
MANAGEMENT
Management of a case of infantile esotropia can
be considered under following heads:
• Clinical evaluation and differential diagnosis
• Non-surgical treatment
• Surgical treatment
• Surgical results and post-surgical treatment
A. Clinical evaluation and differential diagnosis
The essential infantile esotropia usually manifests between birth and 6 months of age and thus
needs to be differentiated from following
conditions:
1. Pseudoesotropia or aparant esotropia may
occur in infants due to following associations:
• Prominent epicanthal folds (Fig. 5.3)
• Small interpupillary distance
• Negative angle kappa, and
• Excessively broad nasal bridge
2. Infantile accommodative esotropia. Though
accommodative esotropia usually occurs
between 2 and 3 years of age but can occur in
infants as young on 2 months of age and is often
diagnosed as infantile esotropia. The key
features which help to differentiate infantile
accommodative esotropia from infantile
(congenital) esotropia are:
• Presence of straight eyes for the first 2–3
months of life,
• Variable angle of strabismus, and
• Hypermetropia >2D.
3. Sensory esotropia may occur rarely in infants
with early onset retinoblastoma and other
disorders of optic nerve and retina.
4. Ciancia syndrome, though a variant of
infantile esotropia, is a distinct clinical entity
characterized by following features:
• Large angle esotropia (>60 PD) with cross-
fixation and both eyes appear to be stuck in
towards the nose.
• Face turn towards fixing eye.
• Limited abduction bilaterally with good
abduction saccades.
• Jerk-end-point nystagmus on attempted
abduction with minimal or no nystagmus on
adduction.
• Tight medial rectus muscle revealed on forced
duction test.
• Vision is most comfortable with the eye in
adduction leading to face turn towards the
fixing eye.
5. Congenital fibrosis syndrome, also known as
strabismus fixus (see page 367) may present as
large angle congenital esotropia with severe
limitation of abduction of one or both eyes. This
is a congenital restrictive strabismus, often
inherited as an autosomal dominant trait.
6. Congenital sixth nerve palsy unilateral or
bilateral also needs to be differentiated from
infantile esotropia.
Clinical work-up which may help in arising at
the diagnosis should include:
1. Examination of anterior segment to rule out
corneal pathology and congenital/developmental cataract.
2. Estimation of visual acuity in an infant can
be made by OKN, PVT or VEP as decribed on
pages 43–44.
3. Examination of fundus and media is quite
useful in diagnosing retinoblastoma and other
abnormalities responsible for sensory squint.
4. Refraction under atropine cycloplegia helps
in discovering refractive accommodative
esotropia due to high hypermetropia. In
essential infantile esotropia, cycloplegic
refraction characteristically reveals only 1–2 D
of hyperopia. Repeat refractions are important
because an accommodative component is
sometimes discovered on follow-up in patients
with infantile esotropia.
5. Measurement of AC/A ratio. The lens gradient
method (see page 127) can be used to know the
approximate AC/A ratio.
6. Measurement of deviation. Usually, an appro-
ximate idea is made by observation for distance
deviation, since it is not possible to get cooperation from the infant for a distance fixation.
However, attempts may be made to measure the
near deviation with the help of Krimsky test
(described on pages 114–115).
7. Differentiation from simulated bilateral sixth
nerve paralysis can be made by Doll's head
phenomenon test, i.e. rotating the child to
demonstrate abduction or by alternate patching
test as described earlier (Fig. 10.2).
Concomitant Esotropias and Exotropias
235
Note. Most of the times, the above examinations
and the typical clinical features are helpful in
establishing the diagnosis of essential infantile
esotropia. Once diagnosed, treatment of choice for
infantile esotropia is surgical alignment of the eyes.
However, some non-surgical treatments may be
needed before the surgery is performed.
B. Non-surgical treatment
Non-surgical measures needed before the
surgery is undertaken include the following:
1. Correction of refractive error. Usually correc-
tion of physiologic hypermetropia of 2D to 3D
has little effect on the deviation. However, it has
been advocated that when hypermetropia is
more than +1.5D, glasses should be prescribed
and child should be reassessed after 6 weeks.
This time it may be possible to determine the
AC/A ratio accurately, because accommodation
will now be controlled by the patient's glasses.
Miotics may be tried as an alternative to
spectacles in unco-operative infants.
2. Treatment of amblyopia. Amblyopia, when
present, should always be treated rigorously
before rather than after the surgery. For
treatment of amblyopia, see page 202. Failure to
treat amblyopia will compromise a stable
surgical alignment of the eyes.
3. Vision therapy: Vision therapy involves a
series of exercises and activities aimed at
training the brain and eyes to work together
more effectively. This approach can be
beneficial, especially in cases where binocular
vision skills are underdeveloped.
C. Surgical treatment
Time of surgery
It has been and still continues to be a controversial
and debatable question. However, experienced
strabismologists have recommended that before
surgery is performed for infantile esotropia,
following prerequists should be ascertained:
• Deviation should be constant and stable.
• Fixation should be alternating or only a mild
fixation preference should be present.
• Accommodative element should be absent.
• Sensory esotropia should have been ruled out.
• Amblyopia should have been treated.
• Associated vertical deviation or A/V patterns
should be revealed.
The above information can be obtained
between the age of 6 months and 2 years
depending upon the cooperation of the child as
well as patience and understanding of the
examiner.
• In general, it has been reported that the sooner
the child can be operated after fulfilling the
above criteria, the better it is.
• Peripheral fusion (monofixation syndrome) is
achieved in most cases (80%), if the surgery is
done by the age of 2 years and in some patients
if it is done by the age of 4 years (20%).
• After the age of 4 years, a functional cure in the
form of peripheral fusion is unlikely.
Choice of surgery
• Bimedial recessions are preferred over the
unilateral recess-resect procedure in the
absence of amblyopia. However, by and large,
it is surgeon's preference.
• It has recently been recognized that a maxi-
mum of 8 mm of medial rectus recession may
be performed without crippling its function
as against the traditionally suggested upper
limit of 5.5 mm.
• Unilateral recess-resect operation on the non-
dominant eye may be performed in patients
who have failed to respond to amblyopia
treatment.
• Amount of muscle surgery to be performed for
horizontal deviation depends upon the
angle of squint, age of the patient, duration of
squint, visual status and the surgeon's previous experience. However, the figures given
in Table 10.1 can serve as a rough guideline for
the beginners. From the Table 10.1, it is clear
that now the surgeon has an alternative to
three and four muscles surgery for a large
angle esotropia.
• Recession of both inferior oblique muscles, if
indicated, should be performed along with the
horizontal muscle surgery.
• Surgical treatment of DVD, if associated
with infantile esotropia, may be postponed for
a later date.
D. Surgical results and post-surgical treatment
Post-surgical treatment will depend upon the
outcome of surgery. Von Noorden has graded