Lectures 1-3 Flashcards
what are the 4 types of visual acuity
detection, resolution, recognition, and direction
what type of visual acuity is used in vision screenings
resoultion
what is physical size measured in
mm or cm
what is visual size measured in
angular units or minarc/secarc
what is the critical detail
(visual size) or 1.0 minarc
what is the overall height
5 times the critical detail (1 x 5 = 1.00minarc)
how big is a basic target at 20ft
8.73mm
if the test distance changes from the standard distance, does the physical size of the target change
it changes
if the test distance changes from the standard distance, does the visual size of the target change
no, it stays the same, (overall height 5.00 minarc and critical detail is 1.00 minarc)
what do you get with the reciprocal of the snellen fraction
the visual size of the critical detail in minarc (20/40 - 40/20= 2.00 minarc)
what is the most common type of anisometropia in children
hyperopia
will accommodation help myopia or hyperopia
hyperopia
what is manifest hyperopia
what is present in a normal eye exam with + lenses in front of eye
what is latent hyperopia
what shows up after cyclo refraction
what is total hyperopia
latent + manifest
what is facultative hyperopia
appears to be 20/20 but is accommodating at distance
what is regular astigmatism
separated by 90 degrees, easily corrected
what is irregular astigmatism
separated by other than 90 degrees apart, poorly corrected
what is muscle tone in the EOMs
pulls the eyes straight ahead, but not the exact amount
what do the EOMs do to make the eyes straight
they are directed by the brain to make up for what the muscle tone lacks
where does the neural signal from each retina combine from the eyes
primary visual cortex
where does fusion occur
in the neocortex
what is sensory fusion
similar targets, similar retinal images, similar locations, properly functioning CNS and motor fusion
what is motor fusion
machinery that controls the contraction of the EOM’s and they are lined up (CNS + cranial nerves + EOMS)
