control of eye movements Flashcards
what one eye movement is disconjugate
vergence (eyes move opposite each other
what is saccidic eye movement
rapid eye movement bringing image onto the fovea
what is the function of smooth pursuit
keeping an image centered on the fovea
what is the function of vestibular-ocular eye movement
holding image steady on fovea during head movements
what is the function of vergence
keeps an image on fovea when object is moved nearer
what structure is the horizontal gaze center
paramedian pontine reticular formation (PPRF)
what CNs are involved in directing horizontal gaze
CN VI - lateral rectus
CN III - medial rectus
what structure is the vertical gaze center
rostral interstitial nucleus of medial longitudinal fasciculus
(riMLF)
what CNs are involved in directing vertical gaze
CN III - superior/inferior rectus
CN IV - superior oblique
what has to happen at the brainstem to initiate saccadic eye movement
burst of excitatory neuron firing
what does the firing of tonic neurons do
initiate the locking and fixing on target in a saccadic eye movement
in a saccadic eye movement, what tells the eye to stop moving once fixed on a target
pause neurons inhibit burst neurons
where are the burst cell bodies for horizontal movement
PPRF
where are the tonic cell bodies for horizontal movement
nucleus prepositus hypoglossi
where are the pause cell bodies for vertical and horizontal movement
omnipause cells of raphe nuclei
where are the burst cell bodies for vertical movement
riMLF
where are the tonic cell bodies for vertical movement
interstitial nucleus of cajal
how can you test a saccadic movements
ask pt to visually jump from one object to another
what are the sxs of a destructive lesion to the frontal gaze center
transient conjugate eye deviation towards lesion
difficulty looking away from lesion
what are the sxs of seizure activity at frontal gaze center
eyes deviate away from firing gaze center
what area is responsible for smooth pursuit
Brodmann area 19 - parieto-occipital jxn
a lesion to what structure will cause a loss of smooth pursuit movements?
parietal lobe - movement toward lesion will be lost
what system is lesioned in a patient whose eyes move in the same direction of head turning (Doll’s eye dysfunction)
vestibular-ocular system (brainstem)
lesion to what structure causes internuclear ophthalmoplegia (INO)
medial longitudinal fasciculus (MLF)
what sxs are associated with INO
weak adduction of ipsilateral eye
abduction nystagmus in contralateral eye
what are the three steps of the near reflex
- convergence (of image on fovea)
- accomodation (lens thickens to focus on fovea)
- pupillary constriction
what is argyll-robertson pupil
symptom of neurosyphilis
-absent light reflex but pupil constricts in near reflex
what is an optokinetic eye movement
smooth pursuit movement w/ sustained head movements
what eye movement are you using when scanning a room for your keys
saccade
what structure initiates voluntary saccade
frontal eye fields (looking for keys)
what structure initiates reflexive saccade
superior colliculus
what is the path of a voluntary horizontal saccade
FEF => contralateral PPRF => contralateral CN VI (lateral rectus) => ipsi CN III (medial rectus)
what structures are near the UPWARD vertical gaze center
superior colliculus
posterior commissure
what condition can cause an upward vertical gaze palsy
pineal tumor
mass compression superior midbrain
what structures are near the downward vertical gaze center
red nucleus
where is the nucleus prepositius hypoglossi and what cells relevant to eye movement are found there
pons
tonic cells for horizontal saccades
where is the interstitial nucleus of cajal and what cells relevant to eye movement are found there
midbrain
tonic cells for vertical saccades
where is the raphe nuclei and what cells relevant to eye movement are found there
reticular formation
pause cells for both horizontal and vertical saccades
if the left FEF fires, initiating a smooth pursuit movement, which direction to the eyes move
left
what will be seen in a patient with a lesion of the parietal lobe when shown optokinetic tape
no nystagmus when tape is move toward lesion
stimulation of the right horizontal semicircular canals results in eye movement in which direction
left
will a patient with INO be able to have vergence
YES
what movement of the eye occurs in convergence
adduction
