[Physiologic and pathologic rebound nystagmus. Description and comparison]

Using a binocular, infrared charged coupled device (CCD), an eye tracker coupled with an Olivetti M24 PC (resolution up to 0.1 degrees, scanning with 80 frames/s), the eye movements of 20 normal individuals with normal visual acuity and binocular function were recorded to detect physiological endpoint (EPN) and rebound nystagmus (RN). Each subject was asked to fixate a target located in the primary position (PP) and after 5 s of recording time, to look at a target either 50 degrees to the right or left of the PP for approximately 20 s and then return for the last few seconds to the PP, EPN recordings were made with the room lights on and RN recordings were made both with the lights on and in total darkness. A forehead and chin rest with bite board were used. Twelve of the 20 subjects showed EPN and RN with the lights on. The 8 subjects that did not demonstrate EPN also showed no RN with the lights on. Recordings from all 20 subjects showed RN in darkness. No differences in amplitude were found between the abducted and adducted eyes. Although clear differences in the characteristics of gaze paretic or drug-related lateral gaze nystagmus and EPN have been found, no systematic differences in RN under lighted conditions had been observed between patients and normal subjects.