L29 Eye Movements Flashcards
What are the 2 types of eye movements
conjugate eye movements (eyes moving together)
non-conjugate eye movements (eyes move in different directions)
what movements fall under conjugate eye movements
saccadic movement/gaze
vestibulo-occular reflex
optokinetic reflex
what is saccadic movement/gaze
voluntary movements
my eyes will “jump” from one point to the next point = scanning a picture
what is the vestibule-occular reflex
uses vestibular system in the event that the head is spun/turned rapidly
keeps my eyes in position of former point of fixation
what is the optokinetic reflex?
utilized in a situation such as watching landscape pass rapidly while I’m in a train
my eyes move rapidly to keep the object of focus in the center of the visual field for as long as possible
what movements fall under non-conjugate movements?
vergence
dysconjugate gaze
what is vergence?
convergence - eyes move towards each other
divergence - eyes move away from each other
what is dysconjugate gaze?
pathological movement pattern -
eyes move erratically and totally independent of each other!
what is the mneumonic for extraocular muscles and the nerves that innervate them
LR6(SO4)3
where is the nerve nuclei for CN III and IV?
midbrain - tegmentum
CN III nuclei at level of SC
CN IV nuclei at level of IC
what is the MLF?
for ascending neurons from abducens nucleus to occulomotor nucleus
what is the role of superior colliculus? what eye movement can it participate in?
receives info from the retinal ganglion cells and can participate in saccadic eye movements
what is MLF essential for
necessary for conjugate eye movement
where is the nerve nuclei for CN VI located?
lower pons
what is the role of PPRF
initial activate CN IV to begin conjugate eye movements (including saccadic eye movements)
where is the vestibular nuclei located
from pons to the MEDULLA
what does the vestibular nuclei control
the vestibulo-ocular reflex
what is the role of the cerebellum (particularly the vestibule-cerebellum) ?
participates in the optokinetic reflex
what is the role of the frontal eye field ?
role in planning and initiation of eye movements (seen in saccadic eye movements)
what brodmanns area corresponds to the frontal eye field?
Area 8
what is the location and role of the parieto-occipital eye field?
at junctions of parietal and occipital lobe
output is involved in depth and motion
what is the purpose of saccadic eye movements
extremely fast movements used to keep the target in focus on the fovea (used for scanning)
how will a trochlear nerve palsy (CN IV) present?
eye = up and in
unopposed IO
how will a occulomotor nerve palsy (CN III) present?
eye = down and out
unopposed LR and SO
how will a abducens nerve palsy (CN VI) present?
eye = medial deviation
unopposed MR
describe diplopia
causes by the fact that an image is landing on different points of the visual field for each eye because one eye is unable to focus the image properly on the fovea
when V1 gets the info - it registers it as actually existing in 2 places = double vision
what is an internuclear ophthalmoplegia
lesion of MLF
abducens n. cannot transmit info to oculomotor n.
so same side MR cannot work
what is a PPRF lesion?
= inability to trigger same abducens n. = inability to initiate and send info up the MLF
