Some individuals who use virtual reality (VR) head-mounted displays (HMD) have adverse visual symptoms.
We measured oculomotor functions of symptomatic (n=10) and asymptomatic (n=10) individuals to determine if there were fundamental oculomotor performance differences. Method. Before and after 20 min of biocular VR- HMD use, we measured: phorias, fixation disparity, gradient accommodative convergence to accommodation ratio (AC/ A), stereopsis, and near point of convergence.
We observed an exophoric shift in the near point phoria of almost all subjects, whereas the farpoint phoria showed no trend. Interestingly, we observed that the phoric shift at far and near was highly correlated for the asymptomatic subjects but not for the symptomatic subjects. In addition, the (stimulus) AC/ A ratio of symptomatic subjects was reduced after a period of VR- HMD use, whereas asymptomatic subjects' AC/ A ratio was not reduced.
The oculomotor changes among the symptomatic subjects (increased exophoria at near and reduced AC/ A) appears consistent with a reduced accommodative response. In contrast, the asymptomatic subjects show changes (correlated change in phorias) which seem most consistent with adaptation in the tonic component of vergence and/ or accommodation