Optokinetic nystagmus is a physiological reflex, initiated by objects moving in a constant direction in the visual field in such a manner as to cause the appearance of a jerking type of nystagmus. The nystagmus consists of a slow or following phase and a rapid recovery phase. This review covers the period from 1954 to the present. For detailed bibliographies prior to 1954, the reader is referred to the usual texts,15,35,77 plus a review of the optokinetic literature from 1946 to 1954 by Kestenbaum.36 Tichy72 reviewed the literature prior to 1956, but Tichy's work is available only in Czech. The Physiology of the Optokinetic Reflex Electronic instrumentation has provided investigators with recording systems, some of them ingenious, for studying eye movements. The photoelectric cell has been used to measure light reflected from retinal vessels19 and thereby extremely fine eye movements; or for more gross measurement the