Squints/ Strasbismus

Question 1

What is stasbismus?

Answer 1

Eyes don’t point in the same direction

Question 2

compare concomitant and incomitant squints

Answer 2

concomitant = angle between eyes is always the same

incomitant = angle between eyes varies depending on gaze

Question 3

compare manifest and latent squints

Answer 3

manifest = apparent when both eyes open and binocular vision used

latent = only present when one eye is shut so monocular vision is being used

Question 4

What is the terminology used for describing squints? Describe a manifest squint with divergent angle using this terminology

Answer 4

manifest = tropia 
latent = phoria 
exo = increased angle between eyes 
endo = reduced angle between eyes 
hypo = downward deviation
hyper = upward deviation

Question 5

What may the presenting complaint and signs be of a child or adult suffering from stasbismus?

Answer 5

• parental worry about appearance
• delay in fine motor and vision milestones
• head tilt, chin lift

In adults they typically cause headaches and double vision

Question 6

What examinations can be using in diagnosing stasbismus? Describe these and what they test for

Answer 6

Hirschberg: shine a light in to the eye and you can see where it reflects

Cover/uncover: focus on an object then cover one eye and watch what the other one dose

Alternate cover: focus on an object and move the cover stick rapidly from one eye to the other, this stops fusion and therefore shows any latent squints

Question 7

On performing the cover/uncover test the eye moves
a) out
b) in
What does this mean?

Answer 7

moves out = esotropia

moves in = exotropia

Question 8

On performing the alternate cover test the eye moves
a) out
b) in
What does this mean?

Answer 8

moves out = esophoria

moves in = exophoria

Question 9

At what age would you want to refer a child with strasbismus?

Answer 9

2 months

Question 10

What are the management options for strasbismus?

Answer 10

• correct the refractive error

- surgical correction if this fails

Question 11

What is accommodative esotropia and who is it seen in?

Answer 11

seen in severe hyperopia they will turn their eyes inwards in order to try and accommodate

Question 12

What causes incomitant squints?

Answer 12

extra-ocular muscle and nerve damage

• RICP
• cavernous sinus thrombosis
• herpes zoster
• myasthenia gravis
• MS
• diabetes and HTN

Question 13

In which direction is the diplopia worst in incomitant squints?

Answer 13

when the patient is trying to move their eye in the direction produced by the paralysed muscle

Question 14

What muscles does CN3 innervate?

Answer 14

• Inferior, superior and medial rectus
• Inferior oblique
• Lavator palpebrae superiorus

The parasympathetics that travel with CN3 innervate the pupillary sphincter and ciliary body

Question 15

What can cause a CN3 palsy? How could you differentiate between these causes?

Answer 15

Pupil sparing: diabetes and vascular disorders leading to ischaemia

Pupil dilated: internal carotid artery aneurysm, posterior communicating artery aneurysm, midbrain stroke, meningitis, uncal herniation

Question 16

What are the signs and symptoms of a CN4 palsy?

Answer 16

• head tilt away from paralysed side

- vertical diplopia worst when looking down and in (reading, walking down stairs)

Question 17

What can cause a CN6 palsy?

Answer 17

RICP due to its long course
HTN and diabetes
Trauma

Question 18

What are the signs and symptoms of CN6 palsy?

Answer 18

• horizontal diplopia on looking to the side of the affected muscles
• can get medial rotation in severe cases