Optically induced eye torsion. I. Fusion cyclovergence.

Fusional cyclovergence was demonstrated for the first time, using ab objective photographic method. It was discovered that the results of subjective and objective measurements of cyclovergence agreed exactly. The largest fusional cyclovergence observed was 8 degrees. The cyclovergence partly cancels out the cyclodisparity presented. The greater part of the cyclodisparity usually remains. The maximum aplitude of the sensory cyclofusion is of the order of 8 degrees. The cyclovergence response is greatest when large fusion images with numerous horizontal contours are presented. The motor mechanism of cyclofusion presupposes the existence of recently demonstrated cyclodisparity detectors. The amplitude of sensory fusion is determined by the vertical diameter of the peripheral Panum areas.