Abstract
We studied horizontal optokinetic nystagmus (OKN) and horizontal optokinetic afternystagmus (OKAN) in five normal human subjects. The cylinder was rotated with an equal velocity of 40°/sec, 60°/sec, 70°/sec, 80°/sec, 90°/sec, 100°/sec. In a dark room, illumination was switched on for 30 sec and then turned off. Eye movements were analyzed by computer. We examined the relationship among averaged retinal slip velocity (RSV, drum velocity minus averaged slow-phase velocity of OKN), slow phase velocity of the first OKAN, duration of OKAN and time constant of the decay of slow phase velocity of OKAN.
We supposed that the most effective RSV for OKAN ranged from 20°/sec to 40°/sec.
We also found that fixation of a small target during optokinetic stimulation almost completely prevented the development of OKAN. We speculated that the target image across the fovea (retinal slip on the fovea) was very important for generation of OKAN.
