Eye Position Shifts Body Sway Under Foot Dominance Bias in the Absence of Visual Feedback

Abstract

Purpose: The purpose of this study was to investigate whether information on extraocular muscle proprioception without visual information affects postural control.

Methods: Thirty-five healthy young volunteers participated in the study. Postural control outcomes included the center of pressure (CoP) for static standing, the total length of the sway of the CoP (LNG), and the sway area (SA), as well as the mean CoP in the mediolateral and anteroposterior directions. The following five eye-fixing positions were used: eye-up (E-Up), eye-down (E-Down), eye-right (E-Right), eye-left (E-Left), and eye-center (Center eye position). One-way ANOVA and Bonferroni correction was performed for statistical processing. Electrooculograms were recorded to detect eye orientation errors, measured with the eyes closed.

Results: The results of this study showed no significant difference between the LNG and SA results when comparing respective eye positions (E-up, E-down, E-right, E-left) relative to E-Center (control). However, the average CoP was shifted to the right at E-Up, E-Down, and E-Left.

Conclusion: These findings indicate that postural control may be affected by eye-body coordination depending on the position of the eyes, even without visual information.

Keywords: body sway; dominant foot; electrooculography; eye position; postural control; visual reference.

Figure 1

Experimental setup and typical EOG waveform. (A) Body sway was measured in a static standing position on a force plate, with no head movement. (B) Eye positions corresponding to E-Up (U), E-Down (D), E-Right (R), E-Left (L), and E-Center (C). (C) Appropriate waveform and (D) inappropriate waveform. A plus sign reflects a shift to the anterior, and a minus sign reflects a shift to the posterior. The waveform is considered inappropriate with an EOG of ±50 μV or higher in a direction different from the target direction. EOG, electrooculography.

Figure 2

LNG, SA, and mean position of the CoP. (A) LNG and (B) SA with the E-Up, E-Down, E-Right, E-Right, and E-Center eye positions. The vertical bars reflect the mean LNG and SA. The error bars indicate the standard error of the mean. (C) The mean CoP position in the ML and AP directions. The solid circles indicate the mean CoP position. The error bars indicate the standard error of the mean. *p < 0.05, ^†p < 0.01. LNG, total trajectory length; SA, sway area; CoP, center of pressure; ML, mediolateral; AP, anteroposterior.