Optokinetic nystagmus (OKN) is often included in a battery of tests to assess central nervous system disorders. Patients with discrete lesions in either the brainstem or the cerebellum showed OKN when the velocity of stimulation was less than 60°/s. The question arises as to whether the range of OKN stimulation we have applied so far (1.2°/s2to 120°/s) is necessary. Therefore, we tried to modify and simplify the OKN test, to steps of constant stimulus velocities at 30°/s, 50°/s, 70°/s and 90°/s and compared the results with those of the OKN tests used previously. The following conclusion can be drawn: 1) The gain of OKN induced by step inputs, with slow phase velocity as a measure, was higher than that of OKN during linear acceleration at each stimulus velocity. 2) Other parameters, such as amplitude and fast phase velocity of OKN showed the same tendency as slow phase velocity. 3) OKN induced by step inputs of constant velocities is a simple and useful test of the function of the oculomotor system.
ASJC Scopus subject areas