Two smaller groups 6M to 1.5M for repetitive testing (20/40, 6/12 to 20/10, 6/3 equiv.). Can be wall-mounted. Includes LogMar and Letter sizes on chart. Equivalents for 20 feet. Logarithmic chart uses traditional Sloan optotypes. These calibrated optotypes blur at threshold and adhere to the Snellen 5×5 grid. Sloan chart uses two smaller groups for repetitive testing and minimizes memorization. Logarithmic Sloan acuity test is a great screener for literate adults and children.