The Pulfrich phenomenon in a large population of young healthy subjects.

Background: To determine whether the Pulfrich phenomenon, an optical illusion occurring in many ophthalmological diseases, is perceived equally in both eyes in a large group of healthy medical students.

Subjects And Methods: A pendulum bob swinging perpendicular to the direction of observation was observed with either the right or the left eye covered with neutral density filters (50, 80 or 90 % absorption) and the apparent elliptical pendulum movement measured in depth. Interocular time delay was calculated from depth.