Ebenholtz (1994) proposed a theory to predict that eye movement is a major cause of visually induced motion sickness (VIMS). In this research, the effects of optkinetic nystagmus (OKN) and optkinetic afternystagmus (OKAN) on VIMS were studied....[ Read more ]

Ebenholtz (1994) proposed a theory to predict that eye movement is a major cause of visually induced motion sickness (VIMS). In this research, the effects of optkinetic nystagmus (OKN) and optkinetic afternystagmus (OKAN) on VIMS were studied.

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 (retinal slip velocity). When watching patterns rotating at 60 degrees per second (dps), increases in retinal slip had been shown to reduce levels of VIMS. In the first part of this thesis, the effects of OKN on VIMS were studied in isolation from the effects of retinal slip velocity. After controlling the confounding effect of increasing retinal slip velocity, reduction of OKN still significantly reduces levels of normalized ratio scale data (p=0.017), mean 7-point nausea rating data (p=0.006) and post SSQ score (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. This supports Ebenholtz (1994)’s theory which predicts that certain eye muscle tractions can elicit signals down the vagus nerves which in turn triggers sickness symptoms commonly found in motion sickness patients.

The second part of the thesis involves a study to characterize the presence of OKAN in viewers exposed to VIMS provoking stimuli. Past studies of OKAN were mostly for the diagnosis of diseases related to vestibular system and no study was conducted to examine the relationships between OKAN and VIMS. Out of the 27 participants, 17 participants (i.e., 63%) exhibited patterns of OKAN. Significant correlations between the time constants of OKAN and levels of VIMS experienced by the same viewers were found (correlation coefficient = 0.584, p=0.017). Further discussions can be found in the thesis.