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Cyril Vienne, Laurent Blondé, Didier Doyen, Pascal Mamassian; Eye movements during vergence effort in stereoscopic ocular pursuit task and their relations to visual fatigue and stereopsis. Journal of Vision 2011;11(11):325. doi: 10.1167/11.11.325.
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© ARVO (1962-2015); The Authors (2016-present)
Stereoscopic viewing of simulated scenes for long durations is getting increasingly popular and it is important to understand the sources of discomfort. It is generally acknowledged that one major problem results from the mismatch between vergence and accommodation cues. This sensory conflict is supposed to entail visual fatigue, while some studies have shown that fatigue could occur even if the depicted stereogram remains in the focus range of the accommodative system, especially in the presence of motion in depth. It is thus unclear why visual fatigue may emerge in absence of strong accommodative demand. To address this question, we evaluated whether visual fatigue might be related, in stereoscopic displays, to the vergence system disturbance. Using a stereoscopic ocular pursuit task to fatigue the visuomotor system, we dynamically measured the accuracy of eye movements. Observers saw a moving-in-depth fixation cross whose displacement was either back to front or front to back relative to the screen plane. This fixation cross was surrounded by a frame composed of small black and white squares to help maintain stereoscopic fusion. Three sessions of stereoscopic ocular pursuit and their control condition were designed according to different convergence demands (±90, 60, 30 and 0 arc minutes of departing/arriving disparity). After each trial, performances in judging the angle of a vertical dihedron in an open-book configuration were assessed using random-dot stereograms. Results revealed that the perception of 3D shape was progressively affected by the strain of the visuomotor task, even when the disparities during the pursuit remained within the focus range. These results overall argue for a potent involvement of in-depth-motion in producing visual symptoms for stereoscopic content. Findings are discussed in light of a sensory-motor hypothesis – which claims that causes of visual fatigue are adaptively motor-dependent –, and of their implications in investigating health-related-questions on traditional stereoscopic displays.
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