Strabismus

Question 1

What is strabismus?

Answer 1

Misalignment of the visual axes of the two eyes.

Question 2

Define binocular single vision (BSV).

Answer 2

The ability to view an object with two eyes, forming two separate images and fusing them centrally into one perception with depth.

Question 3

What is the difference between heterophoria and heterotropia?

Answer 3

Heterophoria is a latent deviation kept latent by fusion reflex, while heterotropia is a manifest deviation where visual axes do not intersect at the fixation point.

Question 4

What is concomitant squint?

Answer 4

A type of manifest squint with constant deviation in all gaze directions and no limitation of ocular movements.

Question 5

What distinguishes incomitant squint from concomitant squint?

Answer 5

Incomitant squint has varying deviation in different gaze directions and could be paralytic, paretic, or restrictive.

Question 6

Name the primary action of the medial rectus muscle.

Answer 6

Adduction.

Question 7

Which nerve innervates the lateral rectus muscle?

Answer 7

The abducent nerve (CN VI).

Question 8

What is the primary action of the superior rectus muscle?

Answer 8

Elevation, maximal when the eye is abducted.

Question 9

What are the subsidiary actions of the inferior rectus muscle?

Answer 9

Adduction and extortion.

Question 10

How does superior oblique action differ when the eye is adducted?

Answer 10

It causes depression and abduction, with depression maximal when the eye is adducted.

Question 11

Define versions in terms of eye movement.

Answer 11

Binocular, simultaneous conjugate eye movement in the same direction.

Question 12

List the six cardinal positions of gaze.

Answer 12

Dextroversion, laevoversion, dextroelevation, dextrodepression, laevoelevation, laevodepression.

Question 13

What is the significance of the nine diagnostic positions of gaze?

Answer 13

They help measure deviations in different gaze positions for accurate diagnosis.

Question 14

What sensory adaptation mechanisms occur with strabismus?

Answer 14

Sensory adaptation includes suppression and abnormal retinal correspondence.

Question 15

What is the role of suppression in sensory adaptation?

Answer 15

Suppression is a sensory adaptation where the brain ignores the image from the deviated eye to avoid double vision.

Question 16

Describe motor adaptations that occur in strabismus.

Answer 16

Face turn, head tilt, chin elevation, or depression.

Question 17

What are the key factors in the aetiology of heterophoria?

Answer 17

Orbital asymmetry, abnormal interpupillary distance, and dissociation factors like monocular tasks.

Question 18

How can uncorrected refractive error lead to concomitant strabismus?

Answer 18

It disrupts accommodation and convergence mechanisms, leading to misalignment.

Question 19

Name a neurogenic cause of incomitant strabismus.

Answer 19

Congenital hypoplasia or aplasia of cranial nerves III, IV, or VI.

Question 20

How does myasthenia gravis affect ocular muscles in strabismus?

Answer 20

Myasthenia gravis causes weakness in the neuromuscular junction, leading to eye muscle weakness and strabismus.

Question 21

What are key points to assess in the history of a patient with strabismus?

Answer 21

Age of onset, variability, direction of deviation, precipitating factors, and family history of strabismus.

Question 22

What is the cover/uncover test used to confirm?

Answer 22

A manifest squint or misalignment.

Question 23

What are the weakening surgical procedures for treating strabismus?

Answer 23

Recession, disinsertion, myotomy, myectomy.

Question 24

What are the strengthening surgical procedures for treating strabismus?

Answer 24

Resection, advancement, tucking.

Question 25

Name an inflammatory lesion that can cause neurogenic incomitant strabismus.

Answer 25

Encephalitis or meningitis.

Question 26

How can face turn be a motor adaptation to strabismus?

Answer 26

It helps the patient avoid diplopia by aligning the eyes to reduce the deviation.

Question 27

Why is early detection of strabismus important in children?

Answer 27

Early detection prevents the development of amblyopia and permanent vision problems.

Question 28

Describe the role of prisms in the treatment of strabismus.

Answer 28

Prisms help realign light entering the eye, aiding in visual fusion.

Question 29

What condition is often treated using botulinum toxin injections in strabismus?

Answer 29

Paralytic strabismus or transient squints.

Question 30

What role does orthoptic exercise play in the management of convergence insufficiency?

Answer 30

It strengthens weak eye muscles, improving binocular vision and alignment.