EVALUATING THE TEST–RETEST RELIABILITY OF FOUR NEWLY DEVELOPED BINOCULAR VISION TESTS

Abstract

Amblyopia will affect 200 million people around the world by 2030 (Fu et al., 2020). Characterized by poor vision, primarily in one eye, this condition arises when an individual does not receive concordant visual input early in life due to strabismus (misalignment of the eyes), cataracts, or high differential refractive error between the two eyes. Due to a lack of normal binocular input early in life, individuals with amblyopia do not develop binocular vision. The disruption of binocular vision prevents accurate depth perception, which causes challenges with everyday tasks such as driving and reading (Levi, Knill & Bavelier, 2015; Birch et al., 2018). Even after corrective surgery, deficits often persist throughout life. Remarkably, in a recent paper by Maehara et al. (2019), a subset of amblyopia patients, who failed all clinical tests of binocular vision, demonstrated a Pulfrich effect. The Pulfrich effect occurs when horizontally moving objects are presented to both eyes with a neutral density filter over one eye. The reduced contrast to the one eye delays visual processing, which the perceptual system perceives as spatial disparity, inducing depth perception. Evidently, binocular vision is necessary to perceive this effect implying these patients have residual hidden binocularity. To explore this phenomenon further, we developed a battery of binocular vision tests (most of which are motion-based). The present project evaluated the test–retest reliability of four tasks: Letter Dominance, Pulfrich, Plaid Motion, and Motion Parallax. Participants with typically developed vision completed these four tasks twice, one week apart. We observed a strong positive correlation between performance on week one and week two for the Letter Dominance, Pulfrich, and Plaid Motion tasks. This represents a foundational step in a research program which aims to obtain more sensitive measures of binocular vision in this population.