Visual acuity, eye movements, motion sickness and the illusion of motion, with optokinetic stimuli

This thesis investigated the correlations between motion sickness, vection, eye movements and visual acuity. Six experiments were conducted. The first compared motion sickness and vection in a real and a virtual reality simulation of an optokinetic drum (with the same filed of view). There was slightly greater motion sickness in the real drum, but no difference in vection. Vection and motion sickness scores did not correlate within conditions, indicating that vection may not be the main cause of motion sickness. It was found that visual acuity was significantly correlated with motion sickness, in both conditions. Subjects with poor acuity reported increased symptoms.In the second experiment subjects viewed a normal optokinetic stimulus on the virtual reality display and the same optokinetic stimulus with a stationary cross in front to the moving strips (fixation). Motion sickness was significantly reduced with fixation but vection was unchanged. Visual acuity was correlated with motion sickness without fixation, as before, but was not correlated with motion sickness with fixation. The fourth experiment found that motion sickness could be produced with a single moving dot, tracked by the eyes of subjects, presented on the virtual reality display. Motion sickness symptoms were not significantly different with a single or multiple dot display. Vection was significantly higher with multiple dots, where peripheral visual stimulation was increased.A fifth experiment found that motion sickness was significantly higher when subjects viewed a standard optokinetic drum without vision correction, compared to viewing with vision correction. Visual acuity and contrast sensitivity to higher spatial frequencies were found to be correlated with motion sickness, indicating that a lack of sensitivity at high spatial frequencies, rather than at a wide range of low and high spatial frequencies, were associated with motion sickness. A final experiment measured the slow phase of nystagmus with and without vision correction. It was found that the slow phase velocity was significantly lower with poorer sensitivity to high spatial frequencies.