Prevalence of disabled stereopsis in a class of optometry students.

Stereopsis is said to be disabled when the third dimension (3-D) cannot be perceived during everyday life but can be when viewing conditions are appropriately arranged. To discover a test suitable for detecting disabled stereopsis, I measured stereoacuity, stereolatency, and the subjective difference in depth perception between monocular and binocular vision of a group of 41 optometry students. Only 2 students showed no sign of this disability. A predictive value for each test was calculated from the results of 14 students whose disability was confirmed by another means. Stereoacuity had the worst predictive value (43%) and stereolatency the best (100%). The prevalence of disabled stereopsis in this group was no less than 34% and might have been as great as 95%.