Visual systems and TBI Flashcards
sight
recognition and location of objects
perception
meaningfulness of what is sighted
lens
inverts and reverses incoming visual information
fovea
central fixation point
photoreceptors
cones and rods
cones
acuity, centrally located around fovea
rods
night vision
blind spot
over the optic disc, where neurons leave the eye
visual pathways
optic nerve> optic chiasm (partial crossing of fibers-nasal)> lateral geniculate of the thalamus, midbrain colliculus (pupil reflex)> primary visual cortex
does the middle eyes cross
yes
do the middle eyes cross
yes
do the outer eyes cross
no
functional categories of eye movement
integration of information from multiple sources, goals of eye movement, gaze stabilization, direction of gaze
goals of eye movement
keep eye stable during head movement, directing gaze at visual targets
direction of gaze
saccades-slow movent side to side
smooth pursuit of conjunction-movt side to side but smooth
vergences: near and far
gaze stabilization
vestibular-ocular, optokinetic
vestibular ocular reflex
action of vestibular information on eyes; with head turns, vestibular system becomes active, information is processed, movement of ocular muscles os stimulates to counter rotation; vertical or horizontal, important for suppress reflex
optokinetic reflex
stabilizes moving images on the retina, static head position
vestibular ocular motor screening (VOMS)
5 assessments
1. smooth pursuits
2. horizontal and vertical saccades
3. convergence
4. horizontal and vertical vestibular occular relfex (VOR)
5. visual motion sensitivity
smooth pursuit
- position object 3’ from subject
- Smooth move the object from the midline to 1.5’ to right and 1.5’ to left
- subject is to follow with eyes without moving head
- sped: should be 2 sec to left and right
(2 reps- 1st R>C>L>C)
repeated vertically
saccades
- hold 2 objects 3’ from patient, place 1.5’ to right and to left
- look from object to object as fast as possible
(do not move head)
-10 reps (1 rep= R>L>R)
repeat vertically 1.5’ above and below midline
convergence
hold the object at arm’s length (14pt font at one end)
have the client bring to face slowly, stop when double vision happens, measure from nose (normally 5cm)
-3 tests
VOMS-accommodation
1eye at time
hold object with text at arms length bring to them with one eye covered, stop when it gets blurry, record (15cm or less is normal) -not if corrected vision
-repeat x3
VOR
hold object 3’ from face, have client focus on object and rotate head 180 beats/min (fast as possible)
(10 reps- 1=back and forth to starting)
wait 10s, symptoms then vertically 1 rep
Visual motion sensitivity
subject stands arms out thumbs up, examiner behind, rotate trunk, arm, head 80 to right and left, maintain gaze on thumb. 5 reps
VOMS results
> 5cm NPC=concussion
anything >2 =concusion
