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M. Kobayashi, T. Fujikado, T. Mihashi; Responses of Accommodation and Vergence to Real or Virtual Dynamic Depth Stimuli. Invest. Ophthalmol. Vis. Sci. 2010;51(13):807.
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© ARVO (1962-2015); The Authors (2016-present)
Recently three dimensional (3-D) display technologies have been extensively developed. In the past, some physiological problems were reported (Yano, Displays, 2002). The 3-D displays with partial depth cues such as retinal disparity are more realistic than those with 2-D displays. However, because the display distance is fixed while the disparity changes, there is a discrepancy between accommodation and vergence. We investigated the responses of accommodation and vergence to dynamic or static stimuli using 3-D or 2-D displays.
Three normal subjects were enrolled in the study. We used a binocular open-view Shack-Hartmann wavefront sensor (Kobayashi, Applied Optics, 2008) to measure accommodation and vergence for 12 seconds. The subject watched the real and the virtual step stimuli (Maltese Cross) in depth, in which the far stimulus was presented at 1500 mm (0.67 D) from the eye and near stimulus was presented at 1250 mm (0.80 D). Far and near stimuli were presented alternatively with durations of 3 seconds. The real step stimuli were presented on two LCD monitors set at far and at near and a half mirror was inserted into the light path between the eye and the monitors. For the virtual stimulus, a 3-D display (X3D Technologies) with a parallax barrier (fine vertical slits) was set at distance 1325 mm (0.75 D) from the eye. Virtual stimuli at the near and at far were presented providing slightly different images to both eyes. We also measured the accommodation and vergence for 30 seconds after changing the stimulus distance from 0.67 D to 1.10 D. We also measured the accommodation and vergence when the subjects observed two different static stimuli on a paper at 0.63 D and at 1.67 D respectively.
The average changes of the accommodation of subject MK, MS and TY were 0.16 D, 0.05 D and 0.02 D respectively to the real target, and 0.12 D, 0.11 D and no response to the virtual target. The average changes of the vergence of subjects MK, MS and TY were 0.27 MA, 0.21 MA and 0.44 MA to the real target, 0.17 MA, 0.19 MA and 0.07 MA to the virtual target. TY accommodated only a very small amount to both real and virtual step stimuli. And he did not accommodate at least for 30 seconds after the distance change of the stimuli although he accommodated reasonably to the real static stimuli.
The change of the accommodation and the vergence in response to the depth stimuli tended to be smaller in the virtual target than in the real target, although individual variation should be taken into account.
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