Effects of Target Size and Test Distance on Stereoacuity

Abstract EN

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.