[The accommodative characteristics of gazing at stereoscopic images on a 3-D display]

We measured the accommodative response in order to investigate the influence of a visual function when gazing at stereoscopic images presented on a three dimensional display.

Accommodative step responses were measured using an infrared optometer, setting the far target at the distance of 1 m and the near target at the distance of 50 cm. The step response of the right eye was examined 6 times at 10-second intervals. The far target was a starburst as a real image and the near target was a white circle on a random dot background on a parallax barrier system three-dimensional display as a stereoscopic image generated with a 90-min arc binocular crossed disparity(+1.5 degrees) and a 90-min arc binocular uncrossed disparity (-1.5 degrees), and a 0-min disparity (0 degree). The near target was presented in 4 ways: 1. -1.5 degrees disparity alone, 2. 0-min disparity alone, 3. +1.5 degrees disparity alone, and 4. +1.5 degrees and -1.5 degrees disparity alternately.

In conditions 1 to 3, the mean +/- standard deviation values of the accommodative response were 0.59 +/- 0.16 D, 0.72 +/- 0.11 D, and 1.03 +/- 0.21 D, respectively. The accommodative response was very large at the disparity of +1.5 degrees compared with the disparity of 0 degree (p = 0.0300). It was not significant although there was a tendency to become small at the disparity of -1.5 degrees (p = 0.0707). In condition 4, the mean +/- standard deviation values of the accommodative response were 0.62 +/- 0.12 D in the condition of -1.5 degrees and 1.03 +/- 0.26 D in condition +1.5 degrees with significant difference (p = 0.0122).

The over accommodation response is induced when gazing at a stereoscopic image under the condition of binocular crossed disparity. This indicates that gazing at stereoscopic images has ill effects on the accommodative system.