MOTION PARALLAX - EFFECTS OF BLUR, CONTRAST, AND FIELD SIZE IN NORMALAND LOW-VISION

Can people with different forms of low vision use motion parallax to i mprove depth judgments? We used a staircase method to compare depth th resholds using motion parallax and static viewing. We tested eighteen normal-vision subjects with a range of simulated deficits in acuity, c ontrast sensitivity, and simulated peripheral-field loss, and ten low- vision subjects with a wide range of acuity, contrast sensitivity, and field loss. Subjects viewed three vertical cylinders monocularly and indicated which one was at a different depth from the other two. For m otion-parallax trials, observers moved their heads (in a viewing assem bly on rollers) from side to side over a range of 6-12 cm. For static trials, the viewing assembly was fixed in place. Normal-vision subject s' depth thresholds with motion parallax were significantly smaller th an those with static viewing by an average factor of 1.95 (p < 0.05) a cross all levels of acuity and contrast. For low-vision observers, the depth thresholds exhibited large individual differences; however, the motion-parallax thresholds were smaller than the static thresholds by an average factor of 2.05 (p < 0.01). These findings indicate that mo tion parallax can provide useful depth information for people with low vision.