Non-reflecting, matte finish eye charts
Designed for vision testing at 20 foot distance
Eye chart measures 24 x 11 in.
The Snellen eye chart was originally introduced in 1862 by Herman Snellen. The Snellen eye test uses the idea of a subtended 5 minutes of arc with a 20 foot distance. This became the "standard vision" measurement. Also, Snellen developed the idea of a 5x5 grid for a standard for his optotypes. Each optotype must meet certain percentage requirements in this grid before it is used for testing. This helps to make a uniform and equal vision chart. The Snellen eye chart is the basis for many other vision tests.