Resumen
Health and safety issues for users of virtual environments can be divided into physiological effects and psychological effects. The physiological effects are best examined by looking at human body systems and mechanisms. Many of the health and safety issues occurring with virtual reality (VR) technology are based in common sense: the occlusion of vision of the real world caused by a display might predispose someone to trip over a cable; other concerns are not so straightforward. For example, motion sickness and motion aftereffects from VR experiences are still not completely theoretically or empirically understood. Of particular interest for those concerned with VR-related health and safety issues are the effects on the visual system of wearing a head-mounted display (HMD). An early study of HMD users suggested that visual acuity was reduced after 20 minutes. Short-term changes such as eyestrain from display systems could occur and changes in ocular alignment might be forced. There are several reasons why eyestrain may occur: the design of the HMD is poor, the user fails to operate it correctly; or the user may have ocular alignment and focusing that is not accommodated by the design of the HMD.