Squint

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Squint
Clinical
Squint (Strabismus)
Hyperphoria and Hypophoria
Strabismus or squint is a
misalignment of visual axis.
One eye forced in out, up
or down. A latent squint
is a phoria. Heterophoria
consists of exophoria,
esophoria, hyperphoria, hypophoria,
cyclophoria. A manifest squint is a tropia.
Hetrotropia is a term which includes all types
of manifest squint.
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Latent Squint
Exophoria and Esophoria are divided into
types according to the distance at which the
phoria is maximum.
Exophoria
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Exophoria of the convergence weakness
types: In which the exophoria measures
more for near than it does for distance.
Exophoria of the divergence excess types:
In which it measures more for distance
than for near.
Exophoria of the basic types: In which the
measurements are the same for near and
distance.
Esophoria
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Esophoria of the convergence excess
types: In which the esophoria measure,
more for near than it does for distance.
Esophoria of the divergence weakness
types: In which it measures more for
distance than for near.
Esophoria of the basic types: In which the
measurements are the same for near &
distance.
Manifest - clear; Intermittent - occuring at regular intervals
A R A V I N D
E Y E
C A R E
S Y S T E M
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It is customary to describe a vertical
phoria for example right hyperphoria
rather than left hypophoria. Most
hyperphoria and are incomitant due to
muscle under action or over action.
The vertical fusion amplitude is normally
small, making it difficult to control more
than a few dioptres of vertical deviation
but exceptions to this rule are occasionally
seen, mainly in long standing deviations.
Cyclophoria
As with cyclotropia, cyclophoria does not
occur alone. When seen it is associated
with hyperphoria but in a rare condition.
Exophoria is by far the most common type of
heterophoria, particularly the convergence
weakness type.
Manifest Squint
All concomitant manifest squint starts in
childhood. The common types of concomitant
squint are exophoria concomitant, esotropia
concomitant. Vertical and torsional squint are
very rare. Both exophoria and esoptropia can
be constant or intermittent.
Manifest Squint – Exotropia
1. Intermittent Exotropia
There are three types,
a. Intermittent Exotropia with divergence
Excess: In which one eye diverges on
distance fixation. The squint is smaller
for near or in the form of a controlled
exophoria.
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b. Intermittent Exotropia with Convergence
Weakness: In which the exotropia is
present for near fixation but is controlled
with exophoria for distance.
c. Basic types: In which the squint is
intermittently manifest for near or
distance. Usually the angle of deviation is
much the same for both distances.
2. Constant Exotropia
The exotropia can be primary, secondary
or corsecutia.
Esotropia: Esotropia can be accommodation
directly related to the exertion of
accommodation or non-accommodative in
which the squint is not influenced by the
amount of accommodation produced.
1. Intermittent Exotropia accommodative
refractive:
a. Fully accommodative esotropia: There is
a moderate degree of hypermetropia. The
esotropia is usually intermittent and is
seen when the child looks at near objects
is tired or unwell. BSV is restored.
b. Accommodative non refractive esotropia :
The squint is present for near fixation but
is controlled
Non - accommodative
a. Non – accommodative convergence
excess: The squint is the same as in
accommodative convergence excess
except that the AC/A ratio is normal.
b. Esotropia with divergence weakness:
Is present for distance fixation with an
esophoria for near fixation. This is also a
rare condition.
the angle of squint but not enough to
restore BSV.
b. Infantile or early onset esotropia :
- Marked esotropia, often measuring 30
prism dioptres or more.
- Alternating esotropia in the primary
position.
- No significant refractive error
c. Late onset esotropia: Onset after 6 months
of age, commonly between 3 years.
d. Secondary esotropia: The squint follows
loss of vision in one eye or more marked
in one eye.
e. Consecutice esotropia: Follows a primary
exotropia. This can result from surgical
correction of exotropia.
Microtropia: A microtropia is very small
manifest squint with BSV; it is a common
condition in which the eye can be esotropic.
Effects of strabismus
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Diplopia confusion, loss of stereopsis
suppression, Amblyopia, Abnormal
retinal correspondence, Compensatory
head posture.
Treatment
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Correcting the refractive correction.
If the squint is slight or
intermittent exercises
an help the patient to
control it.
Patching method
Patching
Surgery
3. Constant Esotropia
a. Partially accommodative esotropia: the
squint is associated with hypermetropia
correction of the refractive error reduces
Before Surgery
After Surgery
- Sr. P.S. Monisha
Refraction, Aravind - Madurai
Compassion July - Sep, 2015