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S Stanger, LS Gray, M Mon-Williams; The Effect of a Virtual Reality Environment Upon Tonic Accommodation and Vergence . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2877.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Stereoscopic virtual reality (VR) displays place unnatural demands upon the near response, requiring 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:20 subjects (mean age 22.14.5 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 infrared autorefractor which takes a measure of the accommodative state every 1s. Readings were taken over a period of 3 minutes 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 minutes using an Eyetrace 300X 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 minutes, generated using SimulEyes field-sequential shutter goggles controlled by a Dell XPS R450 PC. The VR display required a constant accommodation response of 3D, while the vergence response typically varied between 0 and 5MA. Following immersion, measurements of TA and TV were repeated. Results:Mean pre-task TV was 1.893.30MA. The TV became significantly (p<0.005) more divergent as a result of the VR stimulation (mean change -3.585.26MA). In some subjects the divergent shift was substantial. Pre-task TA was 0.410.73D and post-task TA 0.340.70D. This difference was not significant. Conclusion:. The VR environment produced substantial adaptation of TV in the divergent direction. There are no significant changes in TA in the VR environment. These findings suggest that the initial reaction of the accommodation and vergence controllers is to adapt tonic vergence in order to minimise stimuli conflicts found in VR environments, this enables subjects to maintain a stable accommodation response despite continual changes in the vergence position.
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