ABSTRACT
To deal with the effects that virtual environment (VE) technologies might have on users, the categorization of direct versus indirect effects is herein used. Indirect effects affect the user at a high functional level. Indirect effects include psychological effects, such as modification of phobias and enhancement or repression of emotions. Indirect effects also include neurological effects on the visual system (eyestrain, modification of stereoscopic vision, and visual acuity). Virtual environments can also affect the motion detection system and may result in imbalance, nausea, and motion sickness. Research and recommendations into indirect effects including eyestrain and motion sickness are reported in chapters 30 to 32 and 36 to 39 (this volume). Direct effects of VEs are less complex to study and control, but are potentially as great a hazard to users. The direct effects of a VE system are those that act at a direct tissue level, as opposed to the body systems level of the indirect effects. Direct effects are the influence of energy on body tissues from the technology and the risk of trauma because of encumbrances (e.g., weight of a helmet-mounted display [HMD]). Trauma is a particularly important issue, because the essential features of VEs are interactivity and immersion, where the user interacts in three dimensions with computer graphics. Irrational exuberance by users totally absorbed in the virtual experience might occur in some situations and result in injuries. Fortunately, dealing with direct effects of VEs is mostly a matter of common sense and awareness.
