For vision testing at 4 meters (13 ft.)
Acuity range 40M to 2M (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
Louise Sloan developed Sloan optotypes on a principle of equality. Each Sloan letter features many of the same characteristics. They are all calibrated to a 5x5 instead of a 5x4 grid size, giving them a uniform and equal size. Each optotype takes up similar space inside the grid. Also, each letter has very similar difficulty rating. Each line in a Sloan chart balances the 5 optotypes to make the chart the same difficulty from beginning to end. Because Sloan optotypes are so calibrated, vision testing using them is accurate and very reliable.