Relationship Between Ocular Sensory Dominance and Stereopsis

Purpose: It is unknown whether individuals with two balanced eyes show quicker response and lower threshold in fine stereoscopic detection. Previous methods to measure ocular dominance were primarily qualitative, which do not quantify the degree of dominance and show limitation in identifying the dominant eye. In this study, we aimed at quantifying the difference of ocular strength between the two eyes with ocular dominance index (ODI) and studying the association of ocular balance between the two eyes with stereoscopic detection. Methods: Stereoscopic threshold was measured in thirty-three subjects. Stereopsis was measured with random dot stimuli. The minimal detectable disparity (Dmin) and the minimal time needed to acquire the best stereoacuity (Tmin) were quantified. Ocular dominance was measured by a continuous flashing technique with the tested eye viewing a titled Gabor patch increasing in contrast and the fellow non-tested eye viewing a Mondrian noise decreasing in contrast. The log ratio of Mondrian to Gabor’s contrasts was recorded when a subject just detected the tilting direction of the Gabor during each trial. The t-value derived from a t-test of the 50 values obtained in each eye was used to determine a subject’s ODI (ocular dominance index) to quantify the degree of ocular dominance. A subject with ODI ≥ 2 (p < 0.05) was defined to have clear dominance and the eye with larger mean ratio was the dominant eye. Results: The Dmin (55.40 arcsec) in subjects with two balanced eyes were not significantly different from the Dmin (43.29 arcsec) in subjects with clear ocular dominance (p = 0.87). Subjects with two balanced eyes had significantly (p = 0.01) shorter reaction times on average (Tmin = 138.28 msec) compared to subjects with clear dominance (Tmin = 1229.02 msec). Tmin values were highly correlated with ocular dominance (p = 0.0004). Conclusion: Subjects with two relatively balanced eyes take shorter reaction time to achieve optimal level of stereoacuity. Keywords: Ocular Dominance, Local Stereopsis, Binocular, Balanced Eyes, Anisometropia