Two smaller groups 10/25 to 20/8 for repetitive eyesight testing (20/50 to 20/16 equiv.).
Can be wall-mounted.
Sloan optotypes were developed by Louise Sloan in 1959. She developed a set of 10 optotypes that had the same basis as the Snellen optotypes, the 5×5 grid. However, Sloan optotypes do not use serifs and use a geometric progression. This Sloan chart still uses Snellen equivalents and is calibrated for testing at 10 feet.