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Masahiro Ishii; Modulation of distance estimation of visual object by stimulation of vergence and accommodation. Journal of Vision 2014;14(10):140. doi: 10.1167/14.10.140.
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© ARVO (1962-2015); The Authors (2016-present)
The apparent distance can be modulated by vergence alone. The same is true of accommodation. There is conflicting evidence about the effect under the condition in which both of them are varied independently. Here we investigated the role of vergence and accommodation on the absolute distance perception. A stereoscope, 60 cm viewing distance, was used to present dichoptic stimuli. A white square with a black cross-shaped fixation was presented in dark surroundings. The offset between the right eye image and the left eye image was manipulated to vary vergence. A pair of concave or convex lenses was set in front of the eyes to vary accommodation. The size of the image on each monitor was controlled to eliminate the change of image size on the retina caused by the lens. Prior to the experiment, three subjects were trained to give verbal estimates of the distance of a single visual object at different distance. They had normal or corrected to normal vision and normal stereovision. They were in their 20s. In the experiment, the stimulus had an offset to yield vergence of 8.2, 7.2, 6.2, 5.2, or 4.2 degree, and the subject observed through a pair of lenses with -1.75, -1.25, 0, 1.25, or 1.75 diopter. Every offset-lens combination was tested in a random order. Subjects were asked to fixate the center of the target and give the apparent distance verbally. They could spend as much time observing as they wanted. Our results indicated that the offset between the images modulated the perceived distance in agreement with the theoretical value. For lenses, the modulation was about one-tenth of the theoretical value. A similar experiment was conducted with blurred images. The results were similar to that with sharp images.
Meeting abstract presented at VSS 2014
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