Effects of ocular dominance and visual input on body sway.

Purpose: To clarify the role of ocular dominance and to investigate the importance of visual acuity and restriction of the visual field for the visual stabilization of posture.

Methods: The subjects were 31 healthy volunteers ranging in age from 18 to 27 years. The sway of the center of gravity in the upright position was measured by a stabilometer. The tracings of the center of gravity obtained with the stabilometer while the subjects were standing erect for 1 min under several conditions were analyzed. The root mean square (RMS) area of body sway in each case was determined by analysis of the data. The main visual conditions were as follows: with the eyes open; with fixation of the dominant eye or of the nondominant eye; with a binocular or a monocular visual field of 10 degrees; with a binocular or a monocular visual field of 10 degrees and a visual acuity of 0.01; and with the eyes closed.

Results: The main results were as follows: (1) The RMS area while fixation of the dominant eye was maintained was significantly greater than that with fixation of the nondominant eye, and (2) the RMS area showed marked differences between binocular and monocular visual fields restricted to 10 degrees. In monocular fixation of the same visual field, the RMS area increased significantly compared with in binocular fixation.

Conclusions: Binocular vision with the field restricted to 10 degrees offered the greatest contribution to postural stability, but the nondominant eye was more concerned with postural control than the dominant eye.