Patient care

Figures, letters, numbers, or pictures may be used in optotype tests of visual acuity. Traditionally the symbols have been printed on a wall-mounted card and presented to the patient to identify, e.g., the Snellen test. The patient stands at a predetermined distance (usually 20 ft.) from the symbols, covers one eye, and then reads or interprets the symbols for the examiner, and then repeats the process covering the other eye. In illiterate patients or young children directional symbols may be used, e.g., "tumbling E's" instead of numbers or randomly chosen letters of the alphabet. Optotype testing is subject to a number of flaws, e.g., patients may try to memorize listed letters or objects to improve their scores; alternately, some patients with learning disabilities may not understand how to respond to the test.