When we watch a moving object, our lens accommodate on the focused images, our eyes converge to maintain stereo vision, and our pupil controls the amount of light into our eyes. This is called the triple response of eyes. Although virtual reality (VR) binocular displays can present moving stereoscopic images to a viewer, the triple response cannot be performed in a normal fashion because the lens focuses of these displays are fixed. Biological reviews have hypothesized that this may cause eye fatigue in users of VR displays. However, this remains a hypothesis as there is no empirical data to verify it....[ Read more ]

When we watch a moving object, our lens accommodate on the focused images, our eyes converge to maintain stereo vision, and our pupil controls the amount of light into our eyes. This is called the triple response of eyes. Although virtual reality (VR) binocular displays can present moving stereoscopic images to a viewer, the triple response cannot be performed in a normal fashion because the lens focuses of these displays are fixed. Biological reviews have hypothesized that this may cause eye fatigue in users of VR displays. However, this remains a hypothesis as there is no empirical data to verify it.

In this study, a wearable binocular display with dynamically adjustable lens focus has been developed. Two experiments have been conducted to verify the effects of appropriately adjusted lens focus on task performance and eye fatigue. Results of the first (preliminary) experiment show that the time required to form a single stereoscopic image is significantly shorter when the lens focus is adjusted to match with the depth cue of the presented stereoscopic images (p<0.05, paired t-test). In the second (main) experiment, when lens focus is set at 200cm, results show that eye tiredness rating is significantly reduced when stereoscopic images are presented with depth cues appropriate to 200cm rather than 40cm (p<0.01, ANOVA) even though the apparent size of the images presented at a depth of 40cm are larger. This is an important finding because most commercially available VR binocular displays have fixed lens focus of 200cm. This finding can help to explain the commonly reported eye fatigue problems among users of VR displays. Since technological solutions to implement dynamically adjustable lens focus are emerging, the finding of this thesis provides supporting evidence to justify their development.