Abstract:
Purpose: Virtual Reality (VR) headsets create an immersive feeling of presence by displaying images on screens placed centimetres in front of the eyes. A sense of depth is created by imposing a lateral offset to objects presented to each eye. When fixating a close object in virtual space, the eyes converge to maintain a fused image. In the real world, such convergence triggers accommodation, however in VR, convex lenses in front of each eye give the illusion that the screens are fixed at a distance (requiring no accommodative change). Thus, VR headsets can tease out the components of near work which may contribute to myopia, by providing the proximal and convergence near cues, without the accommodative demand. It is unknown whether this disconnect of the accommodative-convergence relationship and the unique optical arrangement in VR negate the risks of myopia development with near work, or the onset of binocular vision abnormalities. Method: We compare binocular vision status (phoria at distance and near, fixation disparity and stability, stereopsis, accommodation) after exposure to either an indoor (near, higher convergence) or outdoor (distance, lower convergence) environment, in both a real and virtual world (n=20x4). We also measured the thickness of the ocular choroid (SS-OCT) before and after exposure, controlling for heart rate and light levels measured during each of the 4 environments. Results: Comparing the change in measures before and after each environmental exposure, we found no change in binocular posture at distance (p = .986) or near (p = .879), gaze stability (p = .323), accommodation (p = .863), or stereopsis (p = .566). However, we did find a significant thickening of the choroid (≈10 microns) after exposure to either virtual reality environment (p < .001), despite no significant difference in heart rate during any of the exposures (p = .152) nor correlation with illumination (p = .852). Conclusions: Comparing real to virtual environments, we found no evidence that VR had an adverse effect on binocular status of the eyes. Indeed, the choroidal thickening which we observed after VR, suggests that a VR headset may not be a myopiagenic stimulus – despite the very close viewing distances involved. To explain the significant choroidal thickening, we propose that the VR headset increased air temperature in the headset, which then increased choroidal blood-flow as a heatsink.