[Analysis of motor response with respect to the time course in cyclofusion]

Torsional eye movements during cyclofusional responses are recorded objectively and analyzed with respect to the time course of the eye movement until the subject perceives a fused image. Eight subjects whose age ranged from 24 to 35 years old were studied. Torsional disparity was presented stepwise by a synoptiscope. The Number of subjects whose motor response was stepped was less than that of the subjects whose motor response was not stepped. The time course of responses varied in individual. Moreover, the number of the subjects whose motor response showed cyclovergence was less than that of subjects whose motor response showed cycloversion. Fusional cyclovergence is reasonable to bring the disparate images within Panum's area efficiently. However our analysis shows that stepped response and cyclovergence is less in number and the motor response is variable in each individual. Therefore, we do not accept the explanation that the cyclofusional motor response simply brings the disparate images within Panum's area. We speculate that cyclofusional motor response is carried out by a feed-back loop through the cyclofusional sensory input to fuse the disparate images.