Comparison of laparoscopic imaging systems and conditions using a knot-tying task.

Pilot experiments to determine the important factors in the engineering of laparoscopic (videoscopic) imaging systems are described in this paper. In the first set of experiments, three videoscopic systems were compared by using a knot-tying task: monoscopic, monoscopic with digital contrast enhancement, and stereoscopic. Direct viewing was used as a control. In both experienced and novice subject groups, no difference was found in completion time or errors between the videoscopic conditions. Performance with direct viewing was significantly better, however, indicating that there are factors in videoscopic imaging that degrade perception or distort the relationship between vision and motor response. In the second set of experiments, the effects of contrast and spatial resolution were examined by varying working distance and camera exposure while experienced subjects tied knots on high- and low-contrast surfaces. Good contrast was found to be most important at longer working distances. This result shows that performance of knot tying, a complex task, is affected by contrast sensitivity, which is a fundamental property of human vision.