Purpose: We have developed a new test suitable for measuring stereopsis in young children and individuals with communication difficulties. It consists of a drifting, computer-generated red and green, dynamic random dot, disparate shape. The motion direction is indicated by the subject (subjective response) or by a naive observer judging the eye movements of the subject (objective response). Disparity is maintained at 616 sec arc and the dependent variable is the angular subtense of the target, which varies from 11 degrees to 11 ft. In this study, precision (ie, measuring repeatability and objective-subjective agreement) and validity were assessed.
Subjects and methods: Sixteen subjects with normal vision participated in the repeatability study and 10 in the validity studies. A two-up/one-down, 2 alternative forced choice staircase procedure was used to measure objective and subjective threshold on two occasions with a 1-week separation. Sensitivity for detecting anisometropia was estimated with simulated anisometropia (0 to 3 D) and by comparison with the Randot test. Sensitivity for detecting amblyopia or strabismus was tested in 10 subjects.
Results: Subjective repeatability was 0.31 log units (2 levels of the test) and objective repeatability was 0.49 log units (3.2 levels of the test). The test was able to detect 2.0 D of simulated anisometropia in 8 of 10 cases (above the 95% confidence interval). None of the amblyopic subjects demonstrated stereopsis.
Conclusion: This test of dynamic global stereopsis has potential as a clinical or screening tool for anisometropia, amblyopia, and strabismus.