Control of Eye Movements

Question 1

Saccadic

Answer 1

Rapid eye movement that brings image of object onto the fovea

Question 2

Smooth pursuit

Answer 2

Keeps a moving image centered on the fovea

Question 3

Vestibular-ocular gaze control

Answer 3

Holds image steady on the fovea during head movements

Controlled by visual pathway and parietooccipital cortex, as well as vestibulocerebellum

Question 4

Vergence

Answer 4

Keeps image on fovea when object is moved near or far away

Deconjugate eye movement- eyes both adduct/abduct

Question 5

Eye movement systems- normal eye movements require

Answer 5

Head movements- vestibular info
Visual objects- vision
Eye movement and position- proprioceptive info
Selection of a visual target- superior colliculus and cortical areas
Medial longitudinal fasciculus MLF also important

Question 6

Optokinetic

Answer 6

Holds images of the target steady on the retina during sustained head rotation- eyes and head moving

Question 7

Saccadic system: Horizontal movement

Answer 7

Frontal eye fields (voluntary movement)- Project fibers to contralateral paramedian pontine reticular formation PPRF (horizontal gaze center), from there projects to CN VI, and then a branch passes through MLF to CN III nucleus 
Superior colliculus (reflexive movement)

Question 8

If right frontal eye fields are stimulated, you will look

Answer 8

Left

Question 9

PPRF lesion (left side)

Answer 9

Unable to look left

Question 10

Saccadic system: Vertical movement

Answer 10

Frontal eye fields project fibers to rostral interstitial nucleus of MLF (miMLF- vertical gaze center), then projects fibers to CN III and IV for upward/downward motion

Question 11

Pineal gland tumor

Answer 11

Will push down near superior colliculus near posterior commissure of brain and give you trouble with vertical saccads

Question 12

Damage to red nucleus near interstitial nucleus of cajal in midbrain

Answer 12

Will have trouble with vertical saccads only when looking downwards

Question 13

Neurons involved in saccadic movement

Answer 13

Burst neuron to get eye there
Tonic neuron to slow down and lock on
Pause neuron to stop on object

Question 14

Location of neurons for horizontal/vertical saccadic movement

Answer 14

Horizontal all located in pons

Vertical all located in midbrain

Question 15

Destructive lesion of frontal eye fields

Answer 15

Transient conjugate eye deviation toward the side of the lesion, difficulty looking away from lesion

Question 16

Seizure/irritating activity in frontal eye field area

Answer 16

Eyes deviating away from the firing gaze center

Look away from irritating, look toward destruction

Question 17

Horizontal and vertical smooth pursuit pathway

Answer 17

Parieto-occipital junction (Brodmanns 19) project fibers to pontine nuclei, then to vestibulocerebellum, then to vestibular nuclei, and then to CN VI and a branch through MLF to CN III
Vertical- same pathway but projects to CN III and IV
If left hemisphere is stimulated, eyes move to the left

Question 18

Optokinetic pathway

Answer 18

Fibers project from visual association cortex, to nucleus of optic tract, then to the pons, then vestibulocerebellum, then vestibular nuclei, then to nuclei of whatever CN you are using

Question 19

Lesion of parietal lobe

Answer 19

Loss of smooth pursuit movement toward the side of the lesion
No optokinetic nystagmus is seen when tape is move towards the affected lob
(optokinetic tape is the tape with a bunch of different shapes

Question 20

Internuclear ophthalmoplegia

Answer 20

Characterized by impaired horizontal eye movements
Results from lesion in MLF in pons/midbrain (seen in MS patients)
-weak adduction of affected eye
-abduction nystagmus (nystagmus when you try to abduct) of the contralateral eye
BL MLF lesion patient trying to look left: cannot abduct left eye without nystagmus, cannot adduct right eye
-patient is able to cross eyes- adduct both at same time

Question 21

Left CN VI lesion

Answer 21

Left eye cant abduct
Right eye cant adduct
(Im guessing because when you look left, the CN VI nucleus also sends fibers to the contralateral CN III nucleus to activate the adductor muscle of that eye, and since the CN VI nucleus is damaged, that doesn’t happen)

Question 22

CN VI nerve palsy

Answer 22

Unable to look left on that side

Question 23

Near reflex pathway (looking cross eyed)

Answer 23

Eyes (visual sight)- Travels through optic nerve to LGN
Fibers leave as optic radiations and travel to primary visual cortex
Travels either to superior colliculus/pre-tectal area (they don’t know which one)
Then travels to CN III nucleus and Edinger-Westphal
Because we bypassed the MLF, you can still use this pathway to adduct both eyes even if you have internuclear ophthalmoplegia

Question 24

Vergence test/pathology

Answer 24

Patient focuses on a near object, near reflex occurs
Argyll-Robertson pupil (caused by neurosyphilis) - absent pupillary light reflex, but pupil constricts in near reflex testing