Effects of Target Size and Test Distance on Stereoacuity

Target size and test distance effects on stereoacuity were investigated in 24 subjects using a three-dimensional monitor. examination 1: target size effects. the test distance was 2.5 m for 0.1�,0.2�,0.5�,and 0.9� target sizes; crossed parallax was presented in 22-second units. average stereoacuity values for 0.1�,0.2�,0.5�,and 0.9� target sizes were 59.58 � 14.86,47.66 � 13.71,41.25 � 15.95,and 39.41 � 15.52 seconds,respectively. stereoacuity was significantly worse with a 0.1� target than with 0.2�,0.5�,and 0.9� target sizes (p = 0.03,p < 0.0001,and p < 0.0001,resp.). examination 2: test distance effects. test distances of 2.5,5.0,and 7.5 m were investigated for a 0.5� target size; crossed parallax was presented in 22-second units. average stereoacuity values at 2.5 m,5.0 m,and 7.5 m test distances were 44.91 � 16.16,34.83 � 10.84,and 24.75 � 7.27 seconds,respectively. stereoacuity at a 7.5 m distance was significantly better than at distances of 2.5 m and 5.0 m (p < 0.0001 and p = 0.02,resp.). stereoacuity at a 5.0 m distance was significantly better than at 2.5 m (p = 0.04). stereoacuity should be estimated by both parallax and other elements,including test distance and target size. � 2016 yo iwata et al.