GA: Control of Eye Mvmts Flashcards
Saccadic, smooth pursuit, vestubular ocular, vergence all all _______.
Supranuclear gaze control systems
Vergence is the only eye mvmt that is?
Disconjugate
Saccadic definition:
A rapid eye mvmt that brings an image of object onto the fovea
like piecing the points of a face together
Keeping a moving image centered on the fovea is called?
Smooth pursuit
Keeping an image steady on the fovea while your head is moving is called?
Vestibular-ocular reflex
What is vergence?
Keeping an image on the fovea when it is moved near (like when you read)
Accomodation (with both eyes) to near targets
Nystagmus requires which control mechanism?
Cortex
What is an optokinetic eye movement?
Holding a target image steady on the retina while your head is rotating
*smooth pursuit w/ head rotation
How would you characterize the Horizontal saccadic system?
- reflexes:
- CN’s:
Frontal eye field + superior colliculus (reflexes) –> PPRF (paramedian pontine reticular formation
CN’s 3+6
How do you describe the Vertical saccadic system?
Frontal eye fields (voluntary) + superior colliculus (reflexes) –> riMLF (rostral interstitial nucleus of the medial lonfitudinal fasciculus)
CN’s 4 + 3
what is the vertical gaze center?
riMLF
What is the horizontal gaze center?
PPRF
What happens if you damage the red nucleus or sup. colliculus?
Vertical gaze palsy:
red nucleus = can’t look up
sup. colliculus = can’t look down
Volitional Saccadic Eye Mvmts
What eye fields contribute towards the reflex of saccadic eye movements (like, if you hear a loud sound, your head turns towards it)?
-Supplementary & parietal eye fields + sup. colliculus
For saccadic eye mvmts, what type of firing moves the eyes towards the target?
excitatory burst neurons
For saccadic eye mvmts, what type of neuronal firing causes the final locking on and fixing on the target?
tonic neurons
Once, the target is locked on (in saccades) what neuron inhibits burst neurons so no further movement occurs?
Pause neurons
For horizontal eye mvmt, what are the burst, tonic, and then pause neurons:
burst: PPRF
tonic: nucleus prepositus hypoglossi (pons)
pause: omnipause cells of ralphe nuclei
In vertical eye mvmts, what are the burst, tonic, and pause cells?
Burst = riMLF
Tonic= interstitial nucleus of cajal (midbrain)
Pause = Ret. Formation (Omnipause cells of Raplhe nuclei)
How do you test for saccadic movements?
Ask patient to visually jump from one object to another
How do destructive lesions and seizure activity affect saccadic eye mvmts:
When you are irritated (seizure) you look away
When you see something destructive (ex. crash) you look towards
If the left hemisphere is activated, which way will the eyes move in smooth pursuit?
To the left
What nuclei are involved in smooth pursuit?
Parieto-occipital JXN
Pontine nuclei + Flocus Nodularis (vestibulocerebellum)
MLF
What is different between the smooth pursit pathway and the optokinetic pathway?
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
A lesion of the parietal lobe will cause:
Loss of smooth pursuit movements toward the side of the lesion
How do you test for smooth pursuit movements?
Patient visually tracks a slow moving object
What is optokinetic tape?
Move tape through fingers in front of patient
In the vestibulo-ocular system, if you head goes right, your eyes go _______.
left
Why does your head turn a different direction from your eyes in the vestibulo-ocular system?
(semicircular canal) Labryinth is activated (in ear)
How can you test for vestibular-ocular movements?
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
What is internuclear opthalmoplegia?
Impaired horizonatal eye movements (affects adduction of affected eye)
What type of lesion causes internuclear opthalmoplegia?
A lesion in the medial longitudinal fasciculus (MLF)
- pons + midbrain
What 3 things happen in the near reflex?
- Convergence (image on fovea)
- Accomodation (lens thickens, so image on fovea)
- Pupillary constriction
What is involved in the near reflex pathway?
Oculomotor nucleus (ADduct)
Edinger-westphal nucles (pupils constrict)
cerebellum
How do you test for vergence?
Have the patient focus on a near object –> the near reflex should occur
What is an Argyll-Robertson pupil (neurosyphilis)?
Absent light reflex (pen light) BUT pupil contstricts in near reflex testing
