The occurrence of virtual simulation sickness symptoms when an HMD was used as a personal viewing system

The effects of using a lightweight HMD as a personal viewing system were examined. When used in this manner, with head-tracking disabled, a sensory conflict which is novel for simulations arises: head movements are detected by the vestibular system but not by the visual system. To investigate the effects of this conflict, ratings of a number of symptoms were reported by 20 subjects before and after they used an HMD for one hour. The results were compared with ratings the same subjects made when viewing a VDU, where the task was the same but the conflict was absent. Of the two conditions, the former produced a significantly greater frequency of increase in the following symptoms: general discomfort, fatigue, headache, nausea, dizziness, stomach awareness, hot or burning eyes, double vision and general visual discomfort. The HMD results were also compared with those from a previous study in which the same headset was used, but configured for VR applications with head-tracking enabled. Surprisingly, given that update lag, cues for vection-induced motion, and accommodation/convergence conflict were all absent, an increase in some symptoms was more frequently reported for the personal viewing configuration. (C) 1997 Elsevier Science B.V.