Abstract
In an attempt to clarify the role of each portion of the peripheral retina in the formation of optokinetic nystagmus, doughnut shaped visual fields were created by means of a visual field separator which has already been described in “Vestibular Mechanisms in Health and Disease”. A variety of sizes of central scotoma and two widths of doughnut, 10 and 20°, were used.
Five healthy persons were tested. The optokinetic stimulation which was used mainly was as follows : 12 black stripes in every 30° were projected and rotated with a constant velocity of 30/sec. The overlapping method was employed for evaluation of the induced optokinetic nystagmus. There was no remarkable difference between the optokinetic nystagmus induced by the doughnut shaped visual fields with central scotomas of 20° and 40°. When the central 60 was covered, the optokinetic nystagmus was hardly elicited.
The width of the doughnut resulted in a slight difference in the elicitation of optokinetic nystagmus.
Thus, the parafoveal retina within 30° is most important for the induction of optokinetic nystagmus. On the other hand, the peripheral retina beyond 30° had a weak influence on the formation of optokinetic nystagmus.
