Types, role and neural control of eye movements

Question 1

Why do we have eye movements?

Answer 1

To achieve clear and stable vision.

Question 2

What are the two principal types of eye movements?

Answer 2

Steady images on the retina: Vestibulo-ocular, optokinetic, smooth pursuit.

Change line of sight: Saccades, vergences.

Question 3

What is the primary function of holding an image on the fovea?

Answer 3

Achieve best visual acuity (VA) and avoid oscillopsia.

Question 4

What is the vestibulo-ocular reflex’s function?

Answer 4

Holds images steady during brief head rotations.

Question 5

What is the optokinetic response?

Answer 5

Holds images steady during sustained head rotation.

Question 6

What is the role of smooth pursuit?

Answer 6

Keeps a moving target on the fovea.

Question 7

What is the function of saccades?

Answer 7

Brings objects of interest onto the fovea.

Question 8

What is vergence?

Answer 8

Moves eyes in opposite directions for single-object focus.

Question 9

What does fixation achieve?

Answer 9

Holds images steady on the fovea for clear vision.

Question 10

What tools assess fixation?

Answer 10

Visuscope and 4 dioptre prism.

Question 11

What is oscillopsia?

Answer 11

Perception of motion due to unstable fixation.

Question 12

Define saccades.

Answer 12

Fast, conjugate eye movements to bring objects into focus on the fovea.

Question 13

What is saccadic suppression?

Answer 13

Prevents blur during saccadic movements.

Question 14

What is the average latency of a saccade?

Answer 14

~200ms.

Question 15

What is the peak velocity range for saccades?

Answer 15

400–700 degrees/second.

Question 16

What is the saccadic main sequence?

Answer 16

Larger saccades have higher peak velocities.

Question 17

What maintains a new eye position after a saccade?

Answer 17

The step, providing tonic innervation.

Question 18

What generates a saccade pulse?

Answer 18

Excitatory burst neurons in the brainstem.

Question 19

Where are horizontal saccades controlled?

Answer 19

Paramedian Pontine Reticular Formation (PPRF).

Question 20

What part of the brain controls vertical saccades?

Answer 20

Rostral interstitial nucleus of the Medial Longitudinal Fasciculus (riMLF).

Question 21

What is smooth pursuit?

Answer 21

Slow tracking movement to maintain objects on the fovea.

Question 22

What stimuli initiate smooth pursuit?

Answer 22

Movement of an object off the fovea.

Question 23

What is the latency of smooth pursuit?

Answer 23

80–120ms.

Question 24

What part of the brain processes moving stimuli?

Answer 24

Middle temporal visual area (MT).

Question 25

What happens in smooth pursuit with unilateral lesions?

Answer 25

Ipsilateral defect.

Question 26

What is the main driver of vergence movements?

Answer 26

Retinal image disparity and blur.

Question 27

What is the latency of disparity-driven vergence?

Answer 27

160ms

Question 28

What controls convergence movements?

Answer 28

Mesencephalic reticular formation and subnuclei at the MR level.

Question 29

What is convergence insufficiency?

Answer 29

Difficulty sustaining convergence, causing diplopia.

Question 30

What is spasm of near reflex?

Answer 30

Overactivation causing variable esotropia and blurred vision.

Question 31

What does the VOR stabilize?

Answer 31

Gaze during brief head movements.

Question 32

What is the latency of VOR?

Answer 32

<15ms.

Question 33

What generates eye movements in VOR?

Answer 33

Hair cells in semicircular canals.

Question 34

What are the VOR abnormalities?

Answer 34

Disequilibrium, vertigo, oscillopsia.

Question 35

What is caloric stimulation?

Answer 35

Tests VOR using warm or cold water in the ear.

Question 36

What is the optokinetic response?

Answer 36

Combines smooth pursuit and saccades for stable vision during sustained movement.

Question 37

What is optokinetic after-nystagmus?

Answer 37

Continued eye movement after stimulus stops.

Question 38

What does the optokinetic drum test?

Answer 38

Full-field stimulus response.

Question 39

What is vestibular nystagmus?

Answer 39

Eye movement caused by vestibular system abnormalities.

Question 40

What is the quick phase of nystagmus?

Answer 40

Fast, repositioning movement during head rotation.

Question 41

What is post-rotational nystagmus?

Answer 41

Nystagmus after head movement stops.

Question 42

How is vestibular nystagmus differentiated?

Answer 42

Present only in the dark (no visual stimuli).

Question 43

What controls horizontal saccades?

Answer 43

Contralateral frontal eye fields (FEF) and parietal cortex.

Question 44

What happens with a PPRF lesion?

Answer 44

Ipsilateral gaze palsy.

Question 45

What is the role of the superior colliculus?

Answer 45

Involved in initiating and directing saccades.

Question 46

What is the role of the cerebellum in eye movements?

Answer 46

Adaptive control and accuracy.

Question 47

How are saccades clinically assessed?

Answer 47

By observing speed, accuracy, and latency.

Question 48

What does an eye tracker measure?

Answer 48

Velocity and peak saccadic movements.

Question 49

What are common smooth pursuit abnormalities?

Answer 49

Initiation defects, low gain, or asymmetry.

Question 50

What is the swinging baby test?

Answer 50

Observes nystagmus and ductions during head rotation.