Ocular Motility

Question 1

Name the 6 extraocular muscles and their primary actions.

Answer 1

Medial Rectus ; in turning (adduction). Lateral Rectus : out-turning (abduction). Superior Rectus : up-turning (supraduction). Inferior Rectus : down-turning (infraduction). Superior oblique : in-twisting (incyclotorsion). Inferior Oblique : out-twisting (excyclotorsion).

Question 2

What are the 6 cardinal positions of gaze?

Answer 2

1. Up and in
2. Up and out
3. Down and in
4. Down and out
5. Straight in
6. Straight out

Question 3

How does the observation of ductions and versions differ?

Answer 3

Versions are tested by observing the eye movements of the patient with both their eyes open. One observes ductions by occluding one eye and observing eye movements of the uncovered eye and then occluding the other eye and observing that eye’s movements.

Question 4

Define suppression.

Answer 4

Suppression is the brain’s mechanism that can develop in young children to avoid double vision (diplopia). When the eyes are not aligned, the brain will ignore or “supress” the image of one eye to prevent diplopia. The not aligned eye is usually the eye that is suppressed. The brain loses this ability after childhood.

Question 5

Define amblyopia.

Answer 5

Amblyopia is decreased vision in one or both eyes due to vision deprivation during early childhood. In conditions like strabismus, congenital cataract, or large refractive states, the young child’s brain does not receive adequate stimulation to develop normal vision and as an adult is uncorrectable by spectacles or contact lenses.

Question 6

What are the limitations of strabismus assessment with corneal light reflex testing?

Answer 6

The corneal light reflex test can be confounded by deformed pupils or abnormal retinal architecture.

Question 7

Which cover test is preformed first and why?

Answer 7

The cover-uncovered test is preformed first because it tests for tropias. Once a tropia is ruled out by the cover-uncover test, the cross cover test (a;ternate cover test) is used to detect a phoria.

Question 8

What is the name of the cover test that measures the amount of strabismus deviation?

Answer 8

Prism and cover test

Question 9

What does the Worth 4-dot test assess?

Answer 9

Fusion, suppression, diplopia

Question 10

What does the titmus test assess?

Answer 10

Depth perception (stereopsis)