GA: Control of Eye Mvmts

Question 1

Saccadic, smooth pursuit, vestubular ocular, vergence all all _______.

Answer 1

Supranuclear gaze control systems

Question 2

Vergence is the only eye mvmt that is?

Answer 2

Disconjugate

Question 3

Saccadic definition:

Answer 3

A rapid eye mvmt that brings an image of object onto the fovea

like piecing the points of a face together

Question 4

Keeping a moving image centered on the fovea is called?

Answer 4

Smooth pursuit

Question 5

Keeping an image steady on the fovea while your head is moving is called?

Answer 5

Vestibular-ocular reflex

Question 6

What is vergence?

Answer 6

Keeping an image on the fovea when it is moved near (like when you read)

Accomodation (with both eyes) to near targets

Question 7

Nystagmus requires which control mechanism?

Answer 7

Cortex

Question 8

What is an optokinetic eye movement?

Answer 8

Holding a target image steady on the retina while your head is rotating

*smooth pursuit w/ head rotation

Question 9

How would you characterize the Horizontal saccadic system?

• reflexes:
• CN’s:

Answer 9

Frontal eye field + superior colliculus (reflexes) –> PPRF (paramedian pontine reticular formation

CN’s 3+6

Question 10

How do you describe the Vertical saccadic system?

Answer 10

Frontal eye fields (voluntary) + superior colliculus (reflexes) –> riMLF (rostral interstitial nucleus of the medial lonfitudinal fasciculus)

CN’s 4 + 3

Question 11

what is the vertical gaze center?

Answer 11

riMLF

Question 12

What is the horizontal gaze center?

Answer 12

PPRF

Question 13

What happens if you damage the red nucleus or sup. colliculus?

Answer 13

Vertical gaze palsy:

red nucleus = can’t look up

sup. colliculus = can’t look down

Question 14

Volitional Saccadic Eye Mvmts

Question 15

What eye fields contribute towards the reflex of saccadic eye movements (like, if you hear a loud sound, your head turns towards it)?

Answer 15

-Supplementary & parietal eye fields + sup. colliculus

Question 16

For saccadic eye mvmts, what type of firing moves the eyes towards the target?

Answer 16

excitatory burst neurons

Question 17

For saccadic eye mvmts, what type of neuronal firing causes the final locking on and fixing on the target?

Answer 17

tonic neurons

Question 18

Once, the target is locked on (in saccades) what neuron inhibits burst neurons so no further movement occurs?

Answer 18

Pause neurons

Question 19

For horizontal eye mvmt, what are the burst, tonic, and then pause neurons:

Answer 19

burst: PPRF
tonic: nucleus prepositus hypoglossi (pons)
pause: omnipause cells of ralphe nuclei

Question 20

In vertical eye mvmts, what are the burst, tonic, and pause cells?

Answer 20

Burst = riMLF

Tonic= interstitial nucleus of cajal (midbrain)

Pause = Ret. Formation (Omnipause cells of Raplhe nuclei)

Question 21

How do you test for saccadic movements?

Answer 21

Ask patient to visually jump from one object to another

Question 22

How do destructive lesions and seizure activity affect saccadic eye mvmts:

Answer 22

When you are irritated (seizure) you look away

When you see something destructive (ex. crash) you look towards

Question 23

If the left hemisphere is activated, which way will the eyes move in smooth pursuit?

Answer 23

To the left

Question 24

What nuclei are involved in smooth pursuit?

Answer 24

Parieto-occipital JXN

Pontine nuclei + Flocus Nodularis (vestibulocerebellum)

MLF

Question 25

What is different between the smooth pursit pathway and the optokinetic pathway?

Answer 25

The optokinetic pathway requires an intact parietooccipital eye field –> becauses the yes make a quick move in the opp. direction in nystagmus

Also, optokinetic = smooth pursuit pathway AND nuclei of accessory optic system

Question 26

A lesion of the parietal lobe will cause:

Answer 26

Loss of smooth pursuit movements toward the side of the lesion

Question 27

How do you test for smooth pursuit movements?

Answer 27

Patient visually tracks a slow moving object

Question 28

What is optokinetic tape?

Answer 28

Move tape through fingers in front of patient

Question 29

In the vestibulo-ocular system, if you head goes right, your eyes go _______.

Answer 29

left

Question 30

Why does your head turn a different direction from your eyes in the vestibulo-ocular system?

Answer 30

(semicircular canal) Labryinth is activated (in ear)

Question 31

How can you test for vestibular-ocular movements?

Answer 31

Doll’s eye maneurver: eyes move in opp. direction of head turning

Ice water caloric test: COWS (have to be awake)

-eye deviates toward the irrigated ear w/ nystagmus

*these will be absent in a coma patient w/ brainstem lesion

Question 32

What is internuclear opthalmoplegia?

Answer 32

Impaired horizonatal eye movements (affects adduction of affected eye)

Question 33

What type of lesion causes internuclear opthalmoplegia?

Answer 33

A lesion in the medial longitudinal fasciculus (MLF)

• pons + midbrain

Question 34

What 3 things happen in the near reflex?

Answer 34

1. Convergence (image on fovea)
2. Accomodation (lens thickens, so image on fovea)
3. Pupillary constriction

Question 35

What is involved in the near reflex pathway?

Answer 35

Oculomotor nucleus (ADduct)

Edinger-westphal nucles (pupils constrict)

cerebellum

Question 36

How do you test for vergence?

Answer 36

Have the patient focus on a near object –> the near reflex should occur

Question 37

What is an Argyll-Robertson pupil (neurosyphilis)?

Answer 37

Absent light reflex (pen light) BUT pupil contstricts in near reflex testing