The relationship between stereopsis and ocular dominance

Purpose:Stereopsis is the highest form of binocular visual processing, in which relative depth information is extracted from two slightly different retinal images. During the process, the visual brain receives and compares the signals sent from the two eyes. However, the two eyes do not always have equal access to the visual brain. Just as hand dominance, ocular dominance, the tendency to prefer visual input from one eye to the other, also exists. It is not clear whether fine stereopsis(lower stereothreshold and quicker response) would only be found in persons with two balanced eyes. This hypothesis has never been tested before because traditional methods to measure ocular dominance were qualitative, which can only identify the dominant eye without showing the degree of dominance. In this study, we set to quantify the relationship between stereopsis and ocular sensory dominance. Methods:Thirty subjects participated in the study. For each subject, ocular dominance was quantified with the continuous flashing technique and ocular dominance index(ODI) was computed. For stereopsis, the stereothresholds were measured with 5 viewing durations ranged from 25 to 400ms. The functions for stereothresholds versus viewing durations were analyzed by an empirical model of quadratic summation, in the form of th= Dmin(t-2+Tmin-2)0.5 where th is the stereothreshold at a given viewing duration(t), Tmin is the constant that determines the horizontal position of the function, which is related to the time at which the stereothreshold becomes independent of duration(critical duration). Dmin is the constant that determines the vertical position of the function and is equal to the stereothreshold when t=Tmin. Results:60% of the subjects showed two relative balanced eyes(ODI \u3c 3db), 29% had moderate ocular dominance(3db≤ODI≤ 9db), and approximately 11% showed strong ocular dominance(ODI\u3e 9db). For subjects with two relatively balanced eyes or moderate ocular dominance, the Dmin values significantly lower than those with strong ocular dominance. Also, the Tmin values were significantly shorter in subjects with two relatively balanced eyes or moderate ocular dominance. Conclusions:People with two relatively balanced eyes tend to have better stereopsis(small Dmin and short Tmin)