Telesurgery by man-machine interaction is currently limited to experimental trials, partly because the visual delay during transmission interferes with the surgeon's hand-eye coordination. The purpose of this study is to examine effect of performance in minute pointing with visual delay. In this experiment, range of visual delay was decided based on previous telesurgery cases, and index of difficulty was prepared based on Fitts law. We conducted tests in which subjects performed pointing operations while visual delay interfered with their hand-eye coordination. The delay levels range from 131 ms to 598 ms by 67 ms. The results showed that Fitts law is able to be applied up to aproximately 500 ms. In addition, it was suggested that another threshold existed between 331 ms and 398 ms. These two thresholds can be considered as changing points of motion strategies.
