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.
Kindergarten Eye Chart is designed for children's visual acuity testing at a distance of 20 feet. This 11" x 24" symbol eye chart is made of extra strong, non-reflecting, matte finish cardboard, with a brass eyelet for wall mounting. Visual acuity notation from 20/200 to 20/10 is also noted in meters.
Description
Snellen and Kindergarten Wall Eye Chart Size 22 x 11 Inch Combo Pack
