Strabismus

Question 1

What is strabismus?

Answer 1

= squint = misalignment of visual axes

Question 2

Describe types of strabismus by aetiology.

Answer 2

• Concomitant (common): due to imbalance in extraocular muscles
- Convergent is more common than divergent
• Paralytic (rare): due to paralysis of extraocular muscles

Question 3

Describe types of strabismus by misalignment.

Answer 3

• Eye turned inwards = esotropia, outwards = exotropia

- Eye turned upwards = hypertropia, downwards = hypotropia

Question 4

How does strabismus cause ambylopia (lazy eye)?

Answer 4

• Brain receives 2 visual images bc of different orientation of eyes
• Brain ignores one image to avoid diplopia
• Poorer vision
• Brain then ‘learns’ to see blurry images with the poorer eye, even with glasses and thus favours one eye

Question 5

What tests must be done to diagnose strabismus?

Answer 5

1. Corneal light reflection test (Hirschberg test)
   
   • Detects squint
   • Light source 30cm away, check for symmetrical reflection of light
2. Cover test
   
   • Identifies nature of squint
   • ask the child to focus on an object
   • cover one eye
   • observe movement of uncovered eyeand covered eye (can still see through proper occlusion)
   • cover other eye and repeat test
   • Movement due to re-fixation

Question 6

What Mx options are there fore strabismus?

Answer 6

1. eye patches may help prevent amblyopia
	• Patching only for equal vision
2. Glasses
	- Helps refocus
3. Surgery (cosmetic only)

Question 7

What red flags are there for more dangerous causes of strabismus?

Answer 7

• Increased ICP
• FHx - retinoblastoma
• NO red reflex i.e. eye problem

Question 8

What are some consequences of strabismus?

Answer 8

• Usually no significant loss to QOL - can still drive
• Ambylopia (lazy eye)
• May lose some depth perception and peripheral vision