Visual Acuity Flashcards
definition of visual acuity
the ability of the visual system to resolve fine detail
what is spatial visual acuity?
the finest spatial detail that can be detected, discriminated, or resolved
detection acuity means the
angular size of the smallest visible target
OD (oculus dexter) = ___ eye
right
OS (oculus sinister) = ___ eye
left
OU (oculus uterque) = ____ eye
both eyes
pinholes can reduce what things?
- reduce effective pupil size
- reduce refractive blur
- reduce illuminance of the retinal image
pinholes can increase what?
increase the depth of field/depth of focus
what are pinholes used for?
to help determine if the reduction in VA is due to uncorrected refractive error or something else
PHNI stands for what? what could this be due to?
pinhole no improvement
-could be non-refractive: ocular disease, amblyopia
what is the “entering VA”?
first test performed at the start of almost every eye exam (medical-legal issue)
snellen chart’s spacing and progression are: regular or irregular?
irregular
in the snellen notation fraction, the numerator is the
testing distance
in the snellen notation fraction, the denominator is the
letter size
definition of “letter size” for senile chart
distance at which the overall letter height subtends 5 minutes of arc