User-Specific Visual Axis Alignment for Reducing Eye Fatigues in HMDs

The pupillary axis and the visual axis in the eye keep a constant angle, which is called “Angle Kappa (K)” [1]. The people with exotropia (the outward deviation of one eye or both eyes) had significantly higher angle kappa than the people with normal eye [2]. Meanwhile, it is also revealed that the people with abnormal binocular vision including strabismus watched stereoscopic images (3D), they showed worse stereoacuity or felt more eye fatigue. It may be because that 3D eye fatigue may be related to kappa angles. This study is based on the hypothesis that 3D eye fatigue can result from kappa angle, the discrepancy between visual axis and the pupillary axis, even though the users do not have strabismus. The purpose of this study is to explore the possibility whether eye fatigue is reduced by matching the participants’ visual axis. First, the app was developed for measuring visual axis with assist of an ophthalmologist. Second, we compared the visual fatigue of participants with and without matching user-specific visual axis alignment. As the result of the objective visual fatigue, divergence hysteresis was significant differently according to the condition of matching visual axis alignment.