Only stereo information improves performance in surgical tasks

Laboratory based research has shown that the use of stereoscopic displays and observer-produced motion parallax in telepresence systems can each improve operators' performance beyond that achieved using conventional 2-D displays. In applied contexts such as minimal access surgery (MAS) tasks are more complex and a range of sources of depth information is available. We therefore decided to examine the benefits of stereoscopic displays and observer-produced motion parallax under more realistic conditions. The 'pick and place' task was taken from surgical performance studies. It involved picking up small irregular spheres from one place and dropping them through apertures in another. The task was performed under seven different viewing conditions: (1) baseline (monocular), (2) biocular, (3) stereoscopic, (4) free motion parallax, (5) instructed motion parallax, (6) augmented motion parallax and (7) stereo and motion parallax. Each subject did a baseline condition (monocular viewing) followed by one of the seven experimental conditions, followed by a final block of the baseline condition (n = 7 conditions x 10 subjects). Only stereoscopic viewing (conditions 3 and 7) leads to better performance. The provision of motion parallax adds nothing to performance. It may even reduce the effectiveness of stereoscopic viewing. The evidence converges on the fact that binocular viewing confers a considerable performance advantage, while providing motion parallax information, to novice operators at least, is not beneficial.