2. It is also known as Strabismus.
It is the deviation of one or both eyeballs due
to problem in the extraocular muscles and
ocular movements
OR
Misalignment of the visual axes of the two eyes
is called squint.
SQUINT
4. Esotropia-inward deviation.
Hypertropia-upward deviation.
Hypotropia-downward deviation.
Incyclotropia-inward/temporal rotation of the
vertical axis of eye.
Excyclotropia-outward/temporal rotation of the
vertical ax
Direction of deviation
Exotropia-outward deviation
6. 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
9. 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
10. 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
11. Constant exotropia. If not treated in time the
intermittent exotropia may decompensate to
become constant exotropia
12. 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
13. 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
14. 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
15. I. History- history is very important. It should
include: age of onset, duration, mode of onset (
sudden or gradual), any illness preceding
squint (fever, trauma, infections, etc.),
intermittent or constant, unilateral or
alternating, history of diplopia, family history of
squint, history of head Lilt or turn and so on.
EVALUATION OF A CASE OF
CONCOMITANT STRABISMUS
16. l. Inspection. Large degree squint (convergent
or divergent) is obvious on inspection.
2. Ocular movements. Both uniocular as well as
binocular movements should be tested in all
the cardinal positions of gaze.
3. Pupillary reactions. These may be abnormal
in patients with sensory exotropia due to
diseases of retina and optic nerve.
Examination
17. 4 . Media and fundus examination. It may
reveal associated disease of ocular media,
retina or optic nerve.
5. Testing of vision and refractive error. It is
most important, because a refractive error
maybe responsible for the symptoms of the
patient or for the deviation itself. Preferably,
refraction should be performed under full
cycloplegia, especially in children.
18. 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
rest should be performed for near fixation (i.e.at
33 cm) as well as distance fixation (i.e. at 6
meter)
Cover Tests
19. 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).
21. 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
23. 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 the re 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.
24. 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.
25. 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
27. 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.
28. 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).
30. 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.
31. 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.
32. 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 :
34. 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
35. 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.
36. 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).
37. • Type and amount of muscle surgery. It depends upon
the type and angle of squint, age of patient, duration of
the squint and the visual status. Therefore, degree of
correction versus amount of extraocuJar muscle
manipulation required cannot be mathematically
determi ned. However, roughly 1 mm resection or medial
rectus (MR) will correct about 2-2.5 PD and 1 mm
recession will correct about 2-3 PD. While I mm resection
and recession of lateral rectus (LR) muscle will correct 2
PD. The maximum limit allowed for MR resection is 8 mm
and recession is 7 mm. The corresponding figures for LR
muscle are 8 mm and 10 mm respectively.
38. 5. Postoperative orthoptlc exercises. These a re
required to improve fusional range and
maintain binocular single vision
