Simulator sickness and HMD configurations

The helmet-mounted display (HMD), often used in non-vehicle-based virtual environments (VEs), can be configured as either a stereoscopic or bi-ocular display. As a stereoscopic display the computer modeling the VE calculates two different views for each eye, based upon the views each eye normally receives due to their separation in the head. On the other hand, the same view can be presented to each eye, resulting in a bi-ocular display. The normally linked processes of accommodation and vergence must be decoupled when viewing through an HMD. This way of perceiving may lead to physiological problems. For example, a common problem with Virtual Environments (VE) is simulator sickness, Its symptoms are similar to those experienced in motion sickness, and include problems with eyestrain, disorientation, and nausea. A study was conducted in which both relative differences in simulator sickness and performance were examined for walking, tracking, distance estimation, and micromanipulation tasks. Using the self-report Simulator Sickness Questionnaire (SSQ), data revealed that the stereoscopic condition was more nauseogenic. In addition, post-experimental Disorientation, Oculomotor Discomfort and Total Severity measures correlated significantly with completion time on a task that required more near-far focal transitions within a short period of time than any other task.