The effect of apparent depth in pictorial images on accommodation

The purpose of this study was to investigate the effect of the apparent depth of pictorial images on accommodation. Steady-state accommodation was assessed objectively while viewing eight pictorial stimuli containing varying degrees of monocular cues to depth. Sixteen young adult subjects were tested monocularly with accommodation either in the closed-loop or open-loop mode. Pictorial depth cues significantly influenced the mean level of accommodation under some of the open-loop conditions in which blur feedback was rendered ineffective. For nearly all stimuli and viewing modes, the mean accommodative responses were biased in the perceptually-appropriate direction, but they were larger in the open-loop condition. Apparent depth cues did not significantly affect accommodation under closed-loop viewing conditions, presumably because blur feedback markedly dampened any perceptually-driven influences. Consistent with current models of accommodation, and several earlier studies, perceptually-based accommodation had only a secondary effect on the overall accommodative response level under naturalistic viewing conditions, with blur dominating.