5. CAUSES
• Congenital, common cause
• High refractive error
• Idiopathic
• Restrictive- due to mechanical restriction in thyroid eye
• Paralytic- paresis of EOM i.e cranial nerve 6
• Sensory
8. Cont..
• Loss of vision in one eye due to injury
• Diseases like corneal opacities, lenticular opacities, optic
atrophy, chorioretinitis (disease 0f the macula)
• Obstruction in pupillary area due to congenital ptosis
• Orbital asymmetry
• Abnormal intrapupillary distance (IPD) wide associated with
exophoria, small with esophoria.
• Faulty insertion of EOM
9. Clinical features
• Ocular deviation
• Ocular movements not limited in any direction
• Refractive error may or may not be associated.
• Suppression and amblyopia may develop.
13. evaluation
History
A careful history is important in the diagnosis
• Birth history, general health and developmental milestones.
• Age of onset of deviation
• Is the deviation constant or intermittent
• Is the deviation present for distance, near or both
• Is it unilateral or alternating
• Is it present when the patient is inattentive or fatigued
14. Cont..
• Is it associated with trauma or physical stress?
• Is there a family history of strabismus
• Are there any other medical problems, headaches, diplopia,
nausea
15. ocular examination
• VA
• For school children and adults, use landolts charts, snelles chart
• For 3-5yrs use matching optotypes, HOTV test, lea charts,
pictorial vision charts.
• For 2-3yrs use dot visual acuity, serial test, toy matching
• 1-2yrs use beads test, ivory balls, preferential looking tests
• 6weeks-1yr use a torch,
• 6weeks and below use indirect assessment eg blinking reflex,
pupillary reactions, visual revocked potential, optokinetic
nystagmus test.
16. 1. 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
secondary deviations due to diseases of retina and optic nerve.
4. Media and fundus examination. It may reveal associated disease of
ocular media, retina or optic nerve.
5. Testing of vision and refractive error.
17. 6. cover tests
i. direct cover test.
• 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)
distance fixation(i.e., at 6 metres).
18. ii. alternate cover test
• It reveals whether the squint is unilateral or alternate and also
differentiates concomitant squint from paralytic squint (where
secondary deviation is greater than primary).
• It is a dissociation test which reveals the total deviation when
fusion is suspended.
• Rt eye is covered for several seconds, the occluder is quickly
shifted to opposite eye for two seconds, then back several times.
After the cover is removed, the examiner notes the speed and
smoothness of recovery as the eyes return to their dissociated
state.
19. 7. Estimation of angle of deviation
i. Hirschberg corneal reflex test.
• It is a rough but handy method to estimate the angle of manifest
squint.
• 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 centre of
pupil is noted in the squinting eye.
• Roughly, the angle of squint is 15o and 45o when the corneal light
reflex falls on the border of pupil and limbus, respectively
20. 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.
21. iii. 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.
22. 8. Tests for grade of binocular vision and sensory
functions
• Normal binocular single vision consists of three grades.
Sensory anomalies include disturbances of binocular vision,
eccentric fixation, suppression, amblyopia, abnormal retinal
correspondence and diplopia.
A few common tests for sensory functions are as follows:
i. Worth’s four-dot test.
ii. Test for fixation.
iii. After-image test.
iv. Sensory function tests with synoptophore.
(v) Neutral density filter test.
23. TREATMENT
GOALS OF TREATMENT. These are to achieve good
cosmetic correction, to improve visual acuity and to
maintain binocular single vision.
i. Spectacles with full correction of refractive error
ii. Occlusion therapy- in cases of amblyopia
iii. Orthoptic exercises- fusion exercises.
iv. Squint surgery
