For testing at 2.5 meters (8.3 ft.)
Acuity range 25.2M to 1.0M (20/200, 6/60 to 20/10, 6/3 equiv.)
Test includes soft-tipped pointer, 50 recording forms (CAT. NO. 2514) and test instructions
Measures 62 X 65 cm (24.5 X 25.5 in.)
CAT. NO. 2425 Illuminator Cabinet is necessary with these translucent low contrast charts
Snellen chart optotypes were one of the first optotype that became standardized for vision testing. They used strong serifs and included several letters that ranged in difficulty. Sloan optotypes were then developed in 1959 using a similar basis. However, these new optotypes excluded serifs. Also, Sloan optotypes closely followed the idea of a 5x5 grid. This grid helped to create an equally difficult group of letters. This helped make vision testing more accurate.