Eye chart 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. 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. 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
The 13th Letter The 13th Letter The 13th Letter is a 1951 American film noir mystery film directed by Otto Preminger. The film is a remake of the French film "Le Corbeau" ("The Raven", 1943) directed by Henri-Georges Clouzot. Doctor Pearson (Michael Rennie), who works at a Canadian hospital in the province of Quebec, receives a series of poison pen letters. More letters, all signed with the mysterious picture of a feather, are delivered to others in the small Canadian town. Cora Laurent (Constance Smith), the wife of the main doctor - Dr. Laurent (Charles Boyer) - at the hospital, receives a letter