Control of Eye Movements

Question 1

Which eye movements are conjugate? (3)

Which eye movements are disconjugate? (1)

Answer 1

Saccadic
Smooth pursuit
Vestibuloocular

Vergence

Question 2

Horizontal/vertical systems do what?

Answer 2

Does rapid eye movements that bring the image of an object onto the fovea so the detail can be seen.

Question 3

Horizontal system tract

Answer 3

1. Frontal eye field and superior colliculus synapses in CL PPRF.
2. PPRF sends a neuron to nucleus VI (CL now).
3. CN VI stays IL to go to LRm. Nucleus VI also sends a fiber to the CL side via MLF to synapse onto nucleus III.
4. CN III goes to MRm.

Question 4

Vertical system tract (simple)

Answer 4

1. Frontal eye field and superior colliculus synapses in riMLF.
2. riMLF sends fibers to CN IV (SOm.) and CN III (IOm.).

Question 5

What 3 things contribute to reflex saccadic eye movements?

Answer 5

Supplementary and parietal eye fields.

Superior colliculus.

Question 6

Burst neurons
Tonic neurons
Pause neurons

Where do these firings occur?

Answer 6

Excitatory firing.
Move eyes toward target.
Inhibit burst neurons to stop further neurons.

Brainstem.

Question 7

Location of Horizontal movements: burst cells, tonic cells, pause cells.

Answer 7

Burst: PPRF
Tonic: nucleus prepositus hypoglossi (pons)
Pause: Raphe nuclei

Question 8

Location of Vertical movements: burst cells, tonic cells, pause cells.

Answer 8

Burst: riMLF.
Tonic: interstitial nucleus of Cajal.
Pause: Raphe nuclei

Question 9

How to test saccadic movements?

Answer 9

Ask pt to visually jump from one object to another.

Question 10

Destructive lesion defects

Answer 10

Eye deviates toward the lesion.

Question 11

In seizure activity, the eyes look:

Answer 11

Away from the firing gaze center.

Question 12

Smooth pursuit purpose

Answer 12

Keeps moving object centered on fovea.

Question 13

Smooth pursuit tract

Answer 13

1. P-O junction goes to pontine nuclei.
2. Pontine nuclei to CL vestibulocerebellum.
3. Vestibulocerebellum to medial vestibular nuclei.
4. Vestibular nuclei send fibers to CL nucleus VI.
5. CN VI goes to IL LRm. and fibers to nucleus III (via MLF).
6. Nucleus III sends CN III to MRm.

*Can also be done in vertical w/ CN III and IV.

Question 14

Optokinetic pathway purpose

Answer 14

Holds image of steady target fixed on retina during head movement.

Question 15

What happens in the optokinetic pathway? (physically, what happens with the eyes?)

Answer 15

Smooth pursuit pathway allows us to remain on target.
Once visual target is broken at limit of visual field, the eyes make a quick move in opposite direction (optokinetic nystagmus).

Question 16

What MUST be intact for the optokinetic pathway to work?

Answer 16

Parietooccipital eye field

Question 17

How to test for smooth pursuit movements:

Answer 17

Optokinetic tape. Move tape through the fingers in front of patient.

Question 18

Lesion of parietal lobe will cause (2):

Answer 18

Loss of smooth pursuit movements toward the side of the lesion.
No optokinetic nystagmus when tape is moved toward damaged lobe.

Question 19

What does doll’s eye maneuver test?

What is the test?

Answer 19

Tests for vestibuloocular movements.

Have pt stay focused on image and move head quickly.

Question 20

Explain COWS

Answer 20

Cold water will cause nystagmus (fast phase) toward opposite side.
Hot water will cause nystagmus toward same side.

Question 21

In a comatose patient, what will the pathology be from doll’s eye maneuver and ice water caloric?

Answer 21

Both reflexes will be absent

Question 22

Internuclear ophthalmoplegia (INO) defects:

What are the able to do, though?

Where is the lesion?

Answer 22

Weak adduction of affected eye (CN III).
Abduction nystagmus of CL eye.

Convergence.

MLF in pons or midbrain.

Question 23

What 3 things occur in the near reflex?

Answer 23

Convergence
Accommodation
Pupillary constriction

Question 24

Argyll-Robertson pupil (neurosyphilis)

Answer 24

Absent light reflex, but pupil constricts in near reflex testing.

Question 25

Pathway of convergence (overview)

Answer 25

1. CN II to LGN.
2. LGN to primary visual cortex.
3. Primary visual cortex to primary association cortex.
4. Primary association nucleus to Edinger Westphal nucleus.

Question 26

Tumors of pineal gland can cause:

Lesions to the red nucleus can cause:

Answer 26

Pineal - upward gaze palsy

Red nucleus - downward gaze palsy