The purpose of this study was to examine the influence of correcting visual acuity and visual fields on upright postural control. Six male and ten female university students who usually wear contact lens participated in this study. A significant difference in visual acuity was found when the participants wore contact lens as opposed to not, but no significant difference in visual acuity between the sexes was found. The participants' Center of Foot Pressure (COP) was measured with and without contact lens, and under three visual field conditions: 1) eyes open in a dark room, 2) central visual field, and 3) complete visual field. The first condition prevents any visual input, the second condition permits gazing at a red lamp fixed in the central visual field in a dark room, and the third condition permits gazing at a visual target fixed in the central visual field with cross-shaped vertical and horizontal lines in a lighted room. To evaluate the COP, we selected 60 parameters representing 7 domains (distance, central position, distribution of amplitude, area, velocity, spectrum and vector).
There was no significant difference in visual properties (visual angle and visual field area) between the sexes, or with the two visual acuity conditions. Therefore, it was considered that correcting visual acuity does not affect visual properties. Based on these results, we examined the differences in COP between the two visual acuity conditions and the three visual field conditions integrating both sexes. There was no significant difference between the two visual acuity conditions in COP. Significant differences in COP parameters between the visual field conditions were found in five domains, excluding "central position" and "area." As a result of multiple comparisons, significant differences in COP parameters were found mainly between "eyes open in a dark room," "central visual field," and "complete visual field." It was suggested that visual input from peripheral visual fields plays an important role in controlling upright posture, and a visual target fixed in the central visual field has little effect on stabilometry.
