Most commonly used for visual acuity testing

Snellen’s chart
Most commonly used for visual acuity testing
Normal visual acuity is 6/6
Distance is 6 m
Reading in Snellen chart
6/60
6/36
6/24
6/18
6/12
6/9
6/6
Interpretation
For eg 6/60 - indicates that what a normal person reads at 60 m , the patient is able to read the same at 6 m
Minimal angle of resolution
Each letter makes an angle of 5 mins of arc at respective distance
Minimal visual acuity recorded by Snellen chart is 1/60
3/60 is cuttoff for blindness

Other charts for visual acuity
Illiterate
E chart
Labdolts C chart

Children
Simple picture chart 2-5 years

Infants
Electro retinography