Strabismus

Question 1

Define strabismus.

Answer 1

A misalignment of the eyes which may cause diplopia and virual confusion.

Question 2

What is the difference between amblyopia and strabismus?

Answer 2

Amblyopia - visual impairment resulting drom abnormal visual stimulation in early childhood

Strabismus - misaligment of the eyes

Amblyopia due to strabismus may be corrected with lenses, patching or atropine of the better-seeing eye.

Question 3

What are the risk factors for strabismus?

Answer 3

• FH
• Prematurity
• LBW
• Maternal smoking during pregnancy
• Refractive error

Question 4

What are the clinical features of strabismus?

Answer 4

Eye misalignment - NB: epicanthal folds, a wide nasal bridge, or eyelid abnormalities may falsely convey the impression of ocular misalignment
Diplopia
Amblyopia

Other:
Asthenopia - ocular discomfort
Other CN palsies - if cause is paralytic strabismus
Abnormal eye movements

Question 5

What are the main two types of strabismus subtypes?

Answer 5

Concomitant (common)
Paralytic (rare)

Question 6

Why is it important to detect strabismus?

Answer 6

Undetected may lead to amblyopia - the brain fails to fully process inputs from one eye and over time favours the other eye

Question 7

What are the causes of concomitant vs paralytic strabismus?

Answer 7

Concomitant - due to imbalance in extraocular muscles, convergent is more common than divergent

Paralytic - due to paralysis of extraocular muscles

Question 8

How do you diagnose strabismus?

Answer 8

Detection of a squint may be made by the corneal light reflection test - holding a light source 30cm from the child’s face to see if the light reflects symmetrically on the pupils

The cover test is used to identify the nature of the squint:

1. ask the child to focus on an object
2. cover one eye
3. observe movement of uncovered eye
4. cover other eye and repeat test

Question 9

What is the management of strabismus?

Answer 9

Refer to secondary care
Correct refractive error - lead to realignment of the eyes in accommodative esotropia (with correction of hyperopia) and some cases of intermittent exotropia.
Eye patches - may help prevent amblyopia; or penalisation of the sound eye by spectacles or atropine 1%

Other:
Extraocular muscle surgery - if no resolution after 6-12 months with other management
Chemodenervation - botulinum toxin A blocking the NMJ of extra-ocular muscles but this is a temporary measure

Question 10

What are the complications of strabismus?

Answer 10

Amblyopia - irreversible loss of vision if not adequately treated
Decreased binocular vision (e.g. depth perception and stereopsis)
Psychosocial problems