__NOTOC__ An<unk> , or optotype, is a chart used to measure visual acuity.<unk> s are often used by health care professionals, such as optometrists, physicians or nurses, to screen persons for vision impairment. Ophthalmologists, physicians who specialize in the eye, also use<unk> s to monitor the visual acuity of their patients in response to various therapies such as medications or surgery. The chart is placed at a standardized distance away from the person whose vision is being tested. The person then attempts to identify the symbols on the chart, starting with the larger symbols and continuing with progressively smaller symbols until the person cannot identify the symbols. The smallest symbols that can be reliably identified is considered the person's visual acuity. The Snellen chart is the most widely used. Alternative types of<unk> s include the logMAR chart, Landolt C, E chart, Lea test, Golovin–Sivtsev table, the Rosenbaum chart, and the Jaeger chart. As previously mentioned,<unk> s measure visual acuity.<unk> s do not provide doctors with information on eye diseases such as glaucoma, problems with the retina, or loss of peripheral vision.
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