Balanced Eyes See Stereopsis More Quickly, but Not More Finely

PURPOSE. To quantify ocular sensory dominance and investigate its relationship to stereopsis. METHOD. A total of 69 subjects participated in the study. Ocular dominance was measured by a continuous flashing technique, with the tested eye viewing a Gabor patch increasing in contrast, and the fellow eye viewing a Mondrian noise decreasing in contrast. In each trial, the log ratio of Mondrian to Gabor’s contrasts was recorded as a subject first detected the Gabor. We collected 50 trials for each eye and an interocular difference was analyzed with a rank-sum test. The z-value was used as the ocular dominance index (ODI) to quantify the degree of ocular dominance. A subject with ODI ≥ 2 was categorized as having a clear ocular dominance, and a subject with ODI < 2 was considered as having balanced eyes (unclear dominance). The stereoacuity was measured with random dot patterns with durations varying from 50 to 1000 ms. The best achievable stereoacuity (Dmin) and the integration time needed to acquire that (Tmin) were calculated. RESULTS. A total of 30 subjects had balanced eyes and 39 had clear ocular dominance. Tmin was significantly longer in subjects with clear ocular dominance than in subjects with balanced eyes (180.18 vs. 121.17 ms, P < 0.01). Tmin was positively correlated with ODI (P < 0.01). However, Dmin in subjects with clear dominance was not different from that in subjects with balanced eyes (40.60 vs. 35.73 arcsec, P = 0.18). CONCLUSIONS. Ocular dominance is not associated with how fine the stereoacuity is, but rather how quickly the best stereoacuity is acquired.