Visual System - Eye Movements

Question 1

Define duction.

Answer 1

Eye Movement in One Eye

Question 2

Define version.

Answer 2

Simultaneous movement of both eyes in the same direction

Question 3

Define vergence.

Answer 3

Simultaneous movement of both eyes in the opposite direction

Question 4

Define convergence.

Answer 4

Simultaneous adduction (inward) movement in both eyes when viewing a near object

Question 5

What is saccade?

Answer 5

• Rapid, conjugate, eye movement

Short fast, burst up to 900 degrees/second
Voluntary and involuntary

Question 6

What are the 4 types of saccade?

Answer 6

• Reflexive saccade to external stimuli
• Scanning saccade
• Predictive saccade to track objects
• Memory guided saccade

Question 7

What is smooth pursuit?

Answer 7

• Sustains slow movement (up to 60 degrees/s)

Driven by motion of a moving target across the retina
Involuntary

Question 8

What are the six extra-ocular muscles?

Answer 8

• Lateral Rectus
• Medial Rectus
• Superior oblique
• Inferior oblique
• Superior rectus
• Inferior rectus

Question 9

Which extra-ocular muscles are innervated by the oculomotor nerve (CNIII)?

Answer 9

• Medial rectus
• Superior rectus
• Inferior Oblique
• Inferior rectus

Question 10

Which nerve innervates the superior oblique?

Answer 10

• Trochlear (CNIV) nerve

Question 11

Which extra-ocular muscle is innervated by the abducens (CNVI) nerve?

Answer 11

• Lateral rectus

Question 12

What is the function of the superior rectus?

Answer 12

• Elevation of the eyeball

Question 13

What is the function of the inferior rectus?

Answer 13

• Depression of the eyeball

Question 14

In what position will the superior rectus elevate the eye maximally?

Answer 14

• Abducted position

Question 15

What is the function of the lateral / external rectus?

Answer 15

• Abduction of the eyeball

Moves eye toward the outside of the head

Question 16

What is the function of the medial rectus?

Answer 16

• Adduction of the eyeball

Moves eye toward the middle of the head

Question 17

What is the function of the superior oblique?

Answer 17

Moves the eye in a diagonal pattern down and out

• Attached high on the temporal side of the eye
• Passes under the Superior Rectus
• Travels through the trochlea

Question 18

What is the function of the inferior oblique?

Answer 18

Elevate and abduct the eye

• Attached low on the nasal side of the eye
• Passes over the Inferior Rectus

Question 19

Which muscle raises the eyelid?

Answer 19

• Levator palebrae superioris

Question 20

Which nerve innervates the levator palpebrae superioris?

Answer 20

• Oculomotor nerve

Question 21

Which specific nerve innervates the superior rectus muscle?

Answer 21

• The superior oculomotor nerve

Question 22

Which specific nerve innervates the medial rectus, inferior rectus and the inferior oblique?

Answer 22

• Inferior oculomotor nerve

Question 23

Which position is the lateral rectus muscle best tested?

Answer 23

• In the abducted position

Question 24

Which position is the medial rectus best tested?

Answer 24

• In the adducted position

Question 25

Which position is the superior rectus best tested in?

Answer 25

* Elevated and abducted position

Question 26

Which position is the inferior rectus best tested in?

Answer 26

* Depressed and abducted position

Question 27

Which position is the inferior oblique best tested in?

Answer 27

* Elevated and adducted

Question 28

Which position is the superior oblique best tested in?

Answer 28

* Depressed and adducted

Question 29

Which muscles assist with convergence?

Answer 29

* **Medial recti**

Question 30

What is the eye movements in a patient with third nerve palsy?

Answer 30

**Down & Out** ## Footnote Unopposed superior oblique innervated by fourth nerve (down) Unopposed lateral rectus action innervated by sixth nerve (out)

Question 31

What happens to the eyelid in a third nerve palsy?

Answer 31

* Ptosis, drooping of the eye lid as the levator palpebrae superioris is affected

Question 32

Which extra-ocular muscles are not affected in a third nerve palsy?

Answer 32

Superior oblique and lateral rectus

Question 33

Which nerve is affected in a sixth-nerve palsy?

Answer 33

* Lateral rectus

Question 34

What happens to eye movements in a sixth nerve palsy?

Answer 34

* Affected eye is unable to abduct and thus deviates inwards

Question 35

What is nystagmus?

Answer 35

Oscillatory movement of the eye

Question 36

What is an optokinetic nystagmus?

Answer 36

Smooth pursuit + Fast phase reset saccade

Question 37

Which eye reflex is useful when testing the visual acuity in pre-verbal children?

Answer 37

Optokinetic nystagmus reflex ## Footnote Observes the presence of nystagmus movement in response to moving grating patterns of various spatial frequencies

Question 38

What is the optokinetic nystagmus reflex?

Answer 38

* Opto-kinetic Nystagmus is a form of physiological nystagmus, triggered by the presentation of a constantly moving grating pattern * The eyes track along the grating motion, with smooth pursuit up to a limit, and resets the eye position to the centre, with a burst of fast saccade motion * **This results in cycles of slow phase smooth pursuit, alternating with fast phase reset saccade in the opposite direction**