Optokinetic nystagmus elicited by a random dot pattern and a wide interval stripe pattern in normal subjects.

In optokinetic stimulus in practical living conditions, not only the central fovea but also the peripheral retina are strongly stimulated. In order to investigate the influence of this stimulus on the peripheral retina in optokinetic nystagmus (OKN), we tested OKN elicited by a pattern of numerous random dots (ROKN) in 30 normal subjects and compared the results with those of OKN elicited by a wide interval stripe pattern. The most significant difference between the two response patterns was the correlation between slow phase velocity and slow and fast phase amplitude. In ROKN, the nystagmus amplitude was highly correlated with slow phase velocity. On the other hand, in SOKN there were two types of correlation between slow phase velocity and nystagmus amplitude. One indicated low correlation, which was extremely predominant, and the other, high correlation as in ROKN. This tendency was more marked in the fast phase amplitude. Although it is generally accepted that OKN fast phase in SOKN is controlled by voluntary saccade, our results indicate that ROKN is more strongly controlled by reflective resetting eye movements, which is similar to the nystagmus fast phase in vestibular nystagmus.