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
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