VAs Flashcards
arc minute
1/60th of a degree
1/60th of a second
Standard revolving power
1 arc minute
recognition
Snellen Chart
patient recognizes a target
detection
ability to detect the presence of an object
usually detecting differences in contrast/brightness in two targets
resolution
resolving two or more targets separated by space more difficult when targets are closer
Lea grating paddles
localization
ability to recognize localization or alignment
Vernier acuity
a form of
recording VA’s of snellen chart
test distance/distance optotype subtends 5 arc minutes
snellen optotype
5 arc min high x 4-5 arc minutes wide
20/20
20 feet test distance/20 feet where the letter on that line subtends 5 arc min
Your patient is 10 feet away (instead of 20 feet) and the lowest line they can read is the 20 /30. what is the snellen equivalent
20/60
Your patient is standing 5 feet away and reads the 20/80 line. What is the snellen equivalent?
20/320
A chart is calibrated for 20 feet is viewed from a distance of 12 feet. the patient can see the 20/40 line. What is the equivalence?
20/67
meter system
used in vision rehabilitation (low vision)
1M optotype sutends 5 arcmin at 1 meter
(1M = 20/50=normal newspaper print)
the patients near VA is 0.2/3M. what is the snellen equivalent?
20/300
Jaeger system
near acuity only
opthamalogy
