Eye chart smaller towards the bottom of the chart. The person removes any glasses or contact lenses, and stands or sits a standardized distance from the chart (e.g., 20 feet for the Snellen chart). The person is then asked to identify the optotypes on the chart, starting with large rows and continuing to smaller rows until the optotypes cannot be reliably identified any more. The row in which the person can reliably identify symbols defines the visual acuity. One eye is tested at a time. Practically, this is accomplished by covering the other eye with a hand, piece of paper, or a
Eye chart visual acuity in infants, young children, and illiterate adults. Special eye charts can be used. One version uses simple pictures or patters. Others are printed with the block letter "E" turned in different orientations, the so-called Tumbling E. The patient simply indicates which direction each "E" is facing. The Landolt C chart is similar: rows have circles with different segments missing, and the test-taker describes where each broken piece is located. The last two kinds of charts also reduce the possibility of the patient guessing the images. Computer-based semi-automatic alternatives to the eye chart have been developed, but are not