Effects of Target Size and Test Distance on Stereoacuity.

Yo Iwata,Hitoshi Ishikawa,Nobuyuki Shoji,Tomoya Handa,Fusako Fujimura

doi:10.1155/2016/7950690

Abstract

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.

Highlights

Stereoacuity tests can be carried out and quickly to detect strabismus and amblyopia and to judge the degree of binocular vision after refractive correction [1–5]
Our results showed that stereoacuity was significantly worse when the target size was 0.1∘
We believe that the reason in cases where the retinal target size and presented parallax were the same is that when the test distance was increased, the projection rate of the stereo target (projection amount from the 3D monitor/test distance × 100) increased

Summary

Introduction

Stereoacuity tests can be carried out and quickly to detect strabismus and amblyopia and to judge the degree of binocular vision after refractive correction [1–5]. There are many differences between stereoacuity test devices used in clinical ophthalmology and movies and attractions that use 3D technology, such as whether they are static or dynamic, the target size, and the test distance. Devices differ in test distance, target size, and binocular separation method [9–15]. In previous studies, there are various opinions about the effect of test distance on stereoacuity as a far stereoacuity test was easier to recognize than near one [25], there was no difference between far and near stereoacuity test [26– 30], and it depended on the subjects [31–33]. The binocular separation method was not consistent, and target size did not necessarily correlate with test distance in previous studies. No previous study has considered both target size and test distance.

Methods

Results

Conclusion