Only standardized format accepted in studies sponsored by the National Eye Institute.
Designed for use in clinical studies and low vision evaluations where accurate, repeatable visual acuity measurements are required.
Lines are of equal difficulty.
Geometric progression in letter size from line to line.
Letter size is only variable.
Can be wall-mounted.
ETDRS charts use a series of three charts with different permutations of optotypes. ETDRS Chart 1 is used to test the right eye’s acuity. ETDRS Chart 2, and Chart R are used to test the visual acuity in the left eye and both eyes, respectively. The use of three ETDRS eye charts to test the visual acuity of one patient prevents memorization and helps increase accuracy and consistency in results.