- For vision testing at 4 meters (13 ft.)
- Acuity range 40M to 2M (20/200, 6/60 to 20/10, 6/3 equiv.)
- 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
- Measures 62 X 65 cm (24.5 X 25.5 in.)
- Can be wall-mounted
The use of ETDRS eye charts,originally used during the first phase of the Early Treatment Diabetic Retinopathy Study and Visual Acuity Impairment Study, has 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.ETDRS (Early Treatment of Diabetic Retinopathy Study) Charts test is designed to eliminate inaccuracies in the Snellen and Sloan tests and have replaced the Snellen and Sloan acuity tests in becoming the worldwide standard in visual acuity testing. The ETDRS test incorporates specific design criteria to make it more accurate than the Snellen or Sloan acuity tests. The four primary criteria include: (1) The same number of letters or symbols per row - five letters or symbols per row (2) There is equal spacing of rows on a log scale. Rows are separated by 0.1 log unit. (3) There is equal spacing of the letters or symbols on a log scale (4) Each row is balanced for letter difficult.
Please Note: Although, several ETDRS charts can be hung on a wall, it is highly recommended to use an ETDRS chart in combination with an approved Illuminated Cabinet.