Oculomotor adaptations produced by virtual reality environments

Publication Summary

Purpose:  Virtual reality (VR) displays require a static accommodation response to be maintained despite continual variation in vergence. The aim of this experiment was to establish the effect of VR stimulation upon the tonic elements of the accommodation and vergence controllers. Methods:  Twenty subjects (mean age 22.0 ± 4.5 years) participated with informed consent in the experiment. The subjects were emmetropic and free of all ocular or systemic disease. Tonic accommodation (TA) was measured in darkness using the Shin-Nippon SRW-5000 (Tokyo, Japan) infrared autorefractor which takes a measure of the accommodative state every 1 s. Readings were taken over a period of 3 min and an average TA value was calculated when the accommodative state had reached a stable level. Tonic vergence (TV) was measured in darkness continuously for 3 min using an EyeTrace 300X (Iota AB, Sundvall, Sweden) infrared limbal eyetracker and an average TV value was calculated when the traces had reached a stable level. Subjects were then immersed in a VR environment, for 30 min, generated using SimulEyes field-sequential shutter goggles controlled by a Dell XPS R450 PC (Bracknell, UK). The VR display required a constant accommodation response of 3D, while the vergence response typically varied between 0 and 5 MA. Following immersion, measurements of TA and TV were repeated. Results:  A significant relationship (y = 1.13x − 0.71, R = 0.85, p = 0.001) was found between the initial TV level and the shift induced by the VR environment such that negative TV positions shifted in the positive direction and vice-versa. No significant change in TA was observed. Conclusions:  The VR environment produced substantial adaptation of TV. These findings suggest that the vergence controller acts to shift vergence bias in order to reduce stimuli conflicts with accommodation found in VR environments. This enables subjects to maintain a stable accommodation response despite continual changes in the vergence position.