2. It is also known as Strabismus.
Definition:
Normally, visual axis of the two eyes are
parallel to each other in the 'primary position of
gaze' and this alignment is maintained in all
positions of gaze.
A misalignment of the visual axes of the two
eyes is called squint or strabismus.
SQUINT
4. It is the type of squint in which the amount of
deviation in the squinting eye remains constant
in all directions and there is no limitation of
ocular movements.
Types:
Convergent squint(esotropia).
Divergent squint(exotropia).
Vertical squint(hypertropia).
COMITANT STRABISMUS
7. It is the inward deviation of one eye.
Esotropia
8. It is characterised by outward deviation of one
eye while other eye fixates.
Classification:
Congenital exotropia .
Primary exotropia.
Sensory exotropia.
Consecutive exotropia.
EXOTROPIA
10. It is rare usually present at birth and almost
always presents before six months of age.
It is characterised by a fairly large and
constant angle of squint, usually alternate with
homonymous fixation in lateral gaze.
Amblyopia is seen in a minority of cases (from
Oto 25 %). Both DVD and IOOA may be
associated with infantile exotropia.
Congenital exotropia
11. It may be unilateral or alternating and may
present as intermittent or constant exotropia.
lntermittent exotropia. It is the most common
type of exodeviation with following features: •
Age of onset is usually early between 2 to 5
years.
• Deviation becomes manifest at times and
latent at others.
Precipitating factors include bright light,
fatigue, ill health and day dreaming.
PRIMARY EXOTROPIA
12. Constant exotropia:
If not treated in time the intermittent exotropia
may decompensate to become constant
exotropia
13. Types. Primary exotropia may be of following
three types:
• Convergence insufficiency type of exotropia is
greater for near than distance,
• Divergence excess type of exotropia is
greater for distance than near, or
• Basic non-specific type exotropia is equal for
near
14. It is a constant unilateral deviation which
results from long-standing monocular lesions
(in adults), associated with low vision in the
affected eye.
Common causes include: traumatic cataract,
corneal opacity, optic atrophy, anisometropic
amblyopia, retinal detachment and organic
macular lesions.
SENSORY EXOTROPIA
15. It is a constant unilateral exotropia which
results either due to surgical overcorrection of
esotropia, or spontaneous conversion of small
degree esotropia with amblyopia into
exotropia.
CONSECUTIVE EXTROPIA
16. i. Direct covertest- lt confirms the presence of
manifest squint.
To perform it, the patient is asked to fixate on a
point light. Then, the normal looking eye is
covered while observing the movement of the
uncovered eye.
In the presence of squint, the uncovered eye will
move in opposite direction to take fixation, while
in apparent squint there will be no movement. This
test should be performed for near fixation (i.e.at
33 cm) as well as distance fixation (i.e. at 6 meter)
Cover Tests
17. ii. Cover-incover Test: One eye is covered with
an occluder and the other is made to fixate on
an object.
In the presence of phoria the eye under cover
will deviate.
The direction of movement of the eye on
removing the cover tells about the type of
heterophoria (the eye moves inwards in cases
of exophoria and outwards in cases of
esophoria).
19. i. Hirschberg corneal reflex test. It is a rough but
handy method to estimate the angle of manifest
squint.
In it, the patient is asked to fixate at point light
held at a distance of 33 cm and the deviation of
the corneal light reflex from the center of pupil is
noted in the squinting eye.
Roughly, the angle of squint is 15° and 45° when
the corneal light reflex falls on the border of pupil
and limb us, respectively and 30° when it lies
between the two.
Estimation of angle of deviation
21. ii. The prism and cover test (prism bar cover test,
i.e. PBCT). Prisms of increasing strength with
apex towards the deviation are placed in front of
one eye and the patient is asked to fixate an
object with the other.
The cover-uncover test is performed till there is
no recovery movement of the eye under cover.
This will tell the amount of deviation in prism
dioptres. Both heterophoria as well as
heterotropia can be measured by this test.
22. ll. Modified Krimsky corneal reflex test. In this
test, the patient is asked to fixate on a point
light and prisms of increasing power ( with
apex towards the direction of manifest squint)
are placed in front of the normal fixating eye till
the corneal light reflex is centred in the
squinting eye.
The power of prism required to centre the light
reflex in the squinting eye equals the amount
of squint in prism dioptres.
23. It is used for screening of squint in infants.
Method:by direct opthalmoscope to illict fundal
red reflex-compare brigthness and intensity in
both eyes.
Equal brightness&colour intensities-Normal
eyes.
Crescent of different colour intensities-
refractive error.
Difference in brightness-Darker eye-
Normal,Brighter eye-Squint.
Bruckner’s Test
25. i. Worth's four-dot test. For this test, patient
wears goggles with red lens in front of the right
and green lens in front of the left eye and views
a box with four lights-one red, two green and
one white.
RESULTS:
A.In normal binocular single vision, the patient
sees all the four lights in the absence of
manifest squint.
Tests for grade of binocular vision
and sensory functions.
26. B. ln abnormal retinal correspondence (ARC),
patient sees four lights even in the presence of
a manifest squint.
C.In right suppression, the patient sees only
three green lights.
D.In alternating suppression, the patient sees
three green lights and two red lights,
alternately.
E•In diplopia, the patient sees five lights (2 red
and 3 green light).
28. Maddox rod test:It is used to measure degree
of phoria at far fixation.
Patient is asked to fix on a point light in the
centre of Maddox tangent scale at a distance
of 6 metres.
A Maddox rod (which consists of many glass
rods of red colour set together in a metallic
disc) is placed in front of one eye(for eg.on left
eye) with axis of the rod parallel to the axis of
deviation.
29. In this case when maddox rod is placed on left
eye:
When patient covers the right eye and look
through lens a striated red line appear.
When patient covers the left eye-sees the
object properly.
30. If Patient sees a red streak with yellow point
source of light in middle-normal eyes.
If patient sees a red streak on the left side and
a yellow point source of light on right side-
uncrossed diplopia seen in Esophoria.
If patient sees a red streak on right side and
yellow source of light on left side-crossed
diplopia seen in Exophoria.
Results :
32. Goals of treatment are:
To achieve good cosmetic correction,
To improve visual acuity, and
To maintain binocular single vision. However,
many time it is not possible to achieve all the
goals in every case
Treatment
33. Treatment modalities. These include the following:
l. Spectacles with full correction of refractive error
should be prescribed in every case. It will improve the
visual acuity and at times may correct the squint
partially or completely (as in accommodative squint).
2. Occlusion therapy. lt is indicated in the presence of
amblyopia. After correcting the refractive error, the
normal eye is occluded and the patient is advised to use
the squinting eye.
Regular follow-ups are done in squint clinic. Occlusion
helps to improve the vision in children below the age of
10 years. (For occlusion regimen.
34. 3. Preoperative orthoptic exercises. These are given
after the correction of amblyo pia to overcome
suppression.
4. Squint surgery. It is required in most of the cases
to correct the deviation. However, it should always
be instituted after the correction of refractive error,
treatment of amblyopia and orthoptic exercises.
•Basic principles of squint surgery.These are to
weaken the strong muscle by recession (shifting the
insertion posteriorly) or to strengthen the weak
muscle by resection (shortening the muscle).
35. 5. Postoperative orthoptlc exercises. These a re
required to improve fusional range and
maintain binocular single vision
