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Abbreviations and symbols commonly used in ophthalmology are listed in the accompanying box.
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1. VISUAL ACUITY (VA)
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Corrected (with glasses, contact lens, or pinhole) distance visual acuity should be tested for each eye in turn, using a Snellen or logMAR (EDTRS) chart. Snellen visual acuity is traditionally measured at 20 feet (6 meters in Europe) or nearer if vision is poor. LogMAR acuity is tested at 13 feet (4 meters), 10 feet (3 meters), or 3 feet (1 meter) when accuracy of test distance and provision of (1 D) refractive correction for presbyopic patients become important. Snellen visual acuity is expressed as a fraction—the test distance over the figure, determined by the distance at which the respective line can be read by a normal individual, assigned to the lowest line the patient can read. If the patient is unable to read the top line even when standing close to the chart, acuity is categorized as counting fingers (CF), hand movements (HM), perception of light (LP), or no light perception (NLP). In general, corrected acuity less than 20/30 (6/9, 0.67) is abnormal but 20/20 (6/6, 1.0) may be abnormal, especially if reduced in comparison to the other eye. LogMAR acuity, which increases as vision deteriorates, is recorded as the total of the values, determined by their size, of all the letters correctly identified with 0.00 being equivalent to 20/20 (6/6, 1.0) and 1.00 being equivalent to 20/200 (6/60, 0.1). For the Visual Acuity Rating (VAR), which decreases as vision deteriorates, each letter identified correctly scores 1, from a baseline of 20/2000 (6/600, 0.01) ...