POSTURAL INSTABILITY INDUCED BY VIRTUAL-REALITY EXPOSURE - DEVELOPMENT OF A CERTIFICATION PROTOCOL

Exposure to virtual environments often causes users to experience symp toms of motion sickness. An accessory manifestation of motion sickness symptoms is postural disequilibrium. If the postural disequilibrium t hat occurs persists beyond the time an individual is within the confin es of the laboratory or system site, user safety could be compromised and products liability issues could be forthcoming. In this study, a p ortable, automated postural assessment system is developed that can be employed before and after exposure to a virtual reality (VR) system i n order to certify that a user's balance on exiting the system is at l east demonstrably as good as it was on entering. It is argued that if the ''coming out'' balance performance is sufficiently poorer than the ''going in'' balance, then the user should be retained until the pret est balance performance is regained. The results from a set of normati ve and validation experiments on postural equilibrium identified sever al reliable measures of stance that could serve as a basis for certifi cation, Furthermore, a new automated video-based measure using only he ad movement showed that performance over sessions is stable and reliab le. The head movement changes that occur with stimuli, such as alcohol and simulator exposure, are well behaved, predictable, and significan t even with small samples. The implication is that the proposed object ive measure of postural stability, in conjunction with procedures for obtaining self-reports of symptoms, can afford some measure of certifi cation that exposure to a given VR system is without harm.