Eye Movements of the Visual System

Question 1

How many muscles innervate the eye?

Answer 1

6

Question 2

What nerves innervate the eye muscles?

Answer 2

CN III (oculomotor)
CN IV (trochlear)
CN VI (abducens)

Question 3

Define duction

Answer 3

Eye movement in one eye

Question 4

Define version

Answer 4

Simultaneous movement of both eyes in the same direction

Question 5

Define vergence

Answer 5

Simultaneous movement of both eyes in the opposite direction to version

Question 6

Define convergence

Answer 6

Simultaneous adduction of both eyes when viewing a near object

Question 7

Define saccades

Answer 7

Short, fast bursts of movement

Question 8

What are the different types of saccades and what do they mean?

Answer 8

Reflexive saccade (to external stimuli)
Scanning saccade
Predictive saccade (to track objects)
Memory guided saccade

Question 9

Define smooth persuit

Answer 9

Sustained slow movements of the eye

Driven by motion of slow moving target acoss retina

Question 10

Where does the superior oblique move the eye?

Answer 10

Down and out

Question 11

Where does the inferior oblique move the eye?

Answer 11

Up and out

Question 12

What muscles does oculomotor innervate?

Answer 12

Superior branch:
Superior rectus and levator palpebrae superioris

Inferior branch:
Inferior and medial rectus, inferior oblique and parasympathetic nerve (pupil constriction)

Question 13

What muscles does trochlear innervate?

Answer 13

Superior oblique

Question 14

What is the role of the lateral rectus?

Answer 14

Moves eye towards the temple

Question 15

What is the role of the medial rectus?

Answer 15

Moves eye towards nasal side of eye

Question 16

What are the prefixes in terms of eye movement for elevation, depression, right and left?

Answer 16

Elevation= supra
Depression= infra
Right= dextro
Left= levo

Question 17

Define torsion as an eye movement

Answer 17

Rotation of eye around the anterior posterior axis of the eye

Question 18

How does the affected eye appear in third nerve palsy- explain why

Answer 18

The eye goes down and out (the lateral rectus and superior oblique are unaffected as they aren’t innervated by CN III) and the eyelid is droopy (the levator palpabrae superioris isnt working)

Question 19

How does the affected eye appear in sixth nerve palsy- explain why

Answer 19

Affected eye cannot abduct because the lateral rectus isnt working so it deviated inwards

Question 20

When does double vision occur in sixth nerve palsy?

Answer 20

When gazing to the side of the affected eye

Question 21

When is the optokinetic nystagmus reflex used and what does it indicate?

Answer 21

It is used to check that there is normal visual acuity in children who can’t speak yet

Question 22

What is optokinetic nystagmus?

Answer 22

Smooth pursuit and fast phase reset saccade