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In stereoscopic extended reality headsets, the distance between optical systems composed of a pair of displays and lenses can be fixed or adjustable. A mismatch between interpupillary distance (IPD) and the distance between optical systems may cause user discomfort and distortions in spatial perception. Nevertheless, little is known about its potential effect on vergence and accommodation. In the study, we explored how visual parameters changed after using the virtual reality headset with a fixed distance between optical systems using routine eye examination tests. Sixty-two subjects (18-33 years of age) were divided into two groups based on the IPD mismatch: 0-5 mm (n = 29) and 6-10 mm (n = 33). Their visual parameters including near point of convergence, amplitude of accommodation, binocular accommodative facility, near horizontal phoria, and fusional reserves were assessed before and after playing 30 minutes of the virtual reality mini-golf game. The data showed considerable changes in the amplitude of accommodation and near point of convergence after the use of virtual reality. Moreover, the prevalence of adverse changes in accommodation and vergence was higher when IPD was mismatched by 6-10 mm compared with the smaller off-alignment. Overall, the findings suggest that the distance between the optical systems in the headsets should be adjustable and matched with the distance between the user’s eyes to lower the demands on the visual system. Moreover, the contribution of IPD mismatch needs to be considered in the user studies investigating the impact of stereoscopic extended reality on the visual system.
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