by covering the other eye with a hand, piece of paper, or a small paddle. After testing without glasses or contact lenses, testing is repeated while the person wears them, if applicable. Often, the use of such refractive lenses will correct visual acuity to normal. Refractive error can be corrected using a pinhole occluder. If the visual acuity improves with the use of pinholes, refractive lenses can be utilized to improve visual acuity. Squinting can achieve the same effect as a pinhole occluder. With the Snellen chart, the visual acuity is recorded as a fraction with 20 in the numerator (top number) and values ranging from 10 to 600 in the denominator (bottom number). The denominator indicates the distance in feet at which a person with normal vision could stand to correctly identify the same symbols identified by the person tested. For example, a visual acuity of 20/20 is considered normal. Variations Numerous types of eye charts exist and are used in various situations. For example, the Snellen chart is designed for use at 6 meters or 20 feet, and is thus appropriate for testing distance vision, while the ETDRS chart is designed for use at 4 meters. There is often also a need to test a subject's vision at near or occupational tasks (such as reading or computer use). For these situations, a Rosenbaum chart or Jaeger chart can be used. While the Snellen chart remains the default, some authors have argued that the logMAR chart is superior. The logMAR chart presents the same number of symbols on each line, uses a typeface with letters that are equally legible at various sizes, and by varying the symbol size logarithmically, it is easier to use at nonstandard distances. As a consequence of these improvements, the logMAR chart has been proposed as a more reliable tool for measuring visual acuity. It can be difficult to measure visual acuity in infants, young children, and illiterate adults. Special eye charts such as Lea Symbols can be used. One version uses simple pictures or patterns. 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