The Effects of Optokinetic Nystagmus on Visually Induced Motion Sickness after the Confounding Effects of Retinal Slip is Controlled

Ebenholtz (1994) predicts that eye movement is a major cause of visually induced motion sickness (VIMS). This paper examines the effects of optkinetic nystagmus (OKN) on VIMS. Past studies had shown that reducing OKN with eye fixation could significantly reduce levels of VIMS. However, the reduction of OKN was confounded with increases in the velocity of image motion projected on viewers' retina (peripherial retinal slip velocity; PRSV). When watching alternating black-and-white vertical stripe rotating at 60 degrees-per-second along the yaw axis, increases in retinal slip velocity have been shown to reduce levels of VIMS (Hu et al., 1989). A within-subject experiment was conducted to study the effects of eye fixation on VIMS with and without the control of the PRSV. After controlling the confounding effect of increasing PRSV, reduction of OKN by eye fixation significantly reduced levels of VIMS as measured by normalized ratio-scale data (p = 0.017), mean 7-point nausea ratings (p = 0.006), and post simulator-sickness-questionnaire scores (p = 0.002). This finding is new and original. It suggests that eye movement by itself rather than its modulating effects on retinal slip velocity is responsible for increases in levels of VIMS. Implications of the results are discussed.