Abstract
Eye fatigue has been considered an important factor when designing visual content for Augmented Reality (AR). For AR devices that have a fixed focal plane, differences between the vergence distance of virtual content and the focal plane could cause eye strain, due to vergence-accommodation conflict (VAC, Shibata, T., Kim, J., Hoffman, D.M. & Banks, M.S., 2011). We investigated the effect of vergence distance on eye fatigue in an experimental setup. Eighteen Participants with normal vision were asked to read a book in an AR head-mounted display (HMD) for 45 minutes. Six participants read content rendered at the same depth as the focal plane (2.5D); six participants read content presented 0.9D farther than the focal plane; the remaining six participants read content presented 1.8D farther than the focal plane. Retinal sizes of panel and font were matched in all three conditions. Before and after reading, participants were asked to rate the fatigue level of their eyes, necks, shoulders and backs. Their accommodation to near and far targets were also measured using a photorefractometer, and showed no change in accommodating to near and far targets after reading. Change of rating in eye fatigue after reading versus before reading showed significant difference between the nearest vergence distance (2.5D) and the furthest distance (0.7D, p=0.05), while there was no difference between the middle distance (1.6D) and the others. There was no difference in fatigue level on other body parts among the three conditions. VAC does not explain the our results since the biggest VAC showed the least eye fatigue. This suggests that in a visually straining task like sustained reading in AR, eye fatigue is dominated by vergence distance, with closer vergence causing the most eye fatigue.
Meeting abstract presented at VSS 2018