Eye chart

NOTOC An eye chart, or optotype, is a chart used to subjectively measure visual acuity. Eye charts 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 eye charts 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 eye charts include the logMAR chart, Landolt C, E chart, Lea test, Golovin–Sivtsev table, the Rosenbaum chart, and the Jaeger chart. As previously mentioned, eye charts measure visual acuity. Eye charts do not provide doctors with information on eye diseases such as glaucoma, problems with the retina, or loss of peripheral vision. In practice, it is very important to recheck the result using Duochrome test, because it allows to refine the final sphere in refraction. It is more important to pass that test, than have perfect binocular vision in Snellen chart, especially for toric contact lenses that may behave differently from glasses. Otherwise binocular fusion may be worse that it is supposed to be. The concept of using eye glasses in order to improve eyesight has been prevalent since the late thirteenth century. As science progressively improved, reputable doctors within the ophthalmology field like Cornelius Donders began to describe a clear definition as to what should be done in order to improve timeless impairments of a patient's vision. Although it slowly became clear what the procedure was in order to benefit a patient through his work, there was no uniform exam in order to prove the impairment in someone’s vision.