Reaction times and the decision-making process in endoscopic surgery

Background: There are times during endoscopic procedures when the displayed surgical field does not align with the actual field due to rotation of the camera. The surgeon’s performance may deteriorate under this situation. However, the effects of misalignment on the decision-making processes during endoscopic procedures have not been fully explored. The present study addresses this problem and suggests a technique that may be used to alleviate it. Methods: Two experiments were completed in a mock endoscopic surgical setup where the image of the work plane inside the training box was either projected on a vertical monitor placed at eye level or superimposed over the training box by means of a half-silvered mirror. The work plane consisted of a start plate and four target plates. The experimenter varied the number of choices of target location among one, two, and four target choices. Rotating the camera about its longitudinal axis misaligned the displayed and the actual work plane. There were two experiments that differed in task difficulty. The task in experiment 1 was to touch the target plate, whereas the task in experiment 2 was to reach, grasp, and transport the object from the target to the start plate. Results: Experiment 1 showed that reaction time increased with the number of the choices for a touch task, in accordance with the Hick-Hyman law. Using a grasp-and-transport task, experiment 2 replicated experiment 1 and extended the results to show that the use of a superimposed image display facilitated the decision-making process, leading to shorter reaction times compared to the vertical image display. Discussion: During endoscopic procedures, the surgeon needs to translate indirect perceptions to instrument-mediated actions by “mapping” them through sensorimotor integration. The superimposed image alleviates the mental load of spatial transformations by reducing the difficulty of the required sensorimotor mapping. These findings have important implications for the design of high-quality superimposed display technologies.