Visual Acuity Flashcards
What is vision acuity?
What the smallest thing you can see at a fixed distance
What is a letter test and what does it measure?
-measures minimum resolvable
- resolve what you see and say it
What is the difference between shnellen and logmar?
-Number of letters on each line
-Spacing
-Scaling
- progression of letter size
- scoring system
What are some qualitative observations?
-fixing and following
-Occlusion of either eye
- fixation preference.
How to test someone?
- Check test distance
- have they got their glasses on?
- have you given instructions?
- occlude one eye
Optokinetic nystagmus (OKN) drum
-this can be used if the child doesn’t respond to any other observation but this helps to see if they can see vision-respond
Teller acuity cards
-test distance (38,55,84cm)
-patient position? ( parent lap, buggy)
-you can do it monocular and binocular
- record results and interpret
. Snellen acuity test
Chart viewing distance/ distance At which a letter
subtends 5
What meters should a snellen chart be done at?
6m
Log mar scoring?
- Each line is 0.1 log mar
- where there are 5 lines/optotypes each is 0.1/5=0.02
How to work out score on log mar test
The line they got correct which is numbered 1.0 you leave but on the next line the ones that they got right u minus them from the top line e.g the top line is 1.0 but they got 2 wrong on the next line so you will do 2x0.02=0.04 so you do 1-0.04=0.06
Snellen acuity chart
-quantitive
-test distance-6m
-age ability- 6+/ knows letters confidently
ETDRS chart - Bailey love
-quantitative, log mar
- test distance: 4m usually
-age ability- 6+/ knows letter confidently
Grating acuity cards
-Quantitative
-grating
-pref looking
-test distance- 38 cm
Cardiff acuity cards
Test distance- 1m or 50cm
Quantitative
Pref looking
Vanishing optotype
