Only standardized vision test 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 vision charts were used during the first phase of the Early Treatment Diabetic Retinopathy Study and Visual Acuity Impairment Study. The use of ETDRS eye charts in these studies have validated their use and has lead to them become the standardized format for testing visual acuity. ETDRS acuity tests are now used in numerous clinical studies worldwide.