The Influence of Binocular Single Vision Intervened Fusional Vergence and Diplopia on The Risk of Falling

Abstract

This study was performed to investigate the influence of visual conditions such as binocular single vision intervened fusional vergence and diplopia on the risk of falls in static posture. Methods: Forty-two subjects of average age 23.40±2.70 years were participated in this study. In order to induce binocular single vision with fusional convergence (FC) and fusional divergence (FD), BI•BO prism lenses of 4Δ and 8Δ were added, respectively, and to induce vertical vergence (VV), OD-BU 1Δ/OS-BD 1Δ was added in a trial frame fully corrected subject's refractive error. We detected the minimum amount of prism that diplopia was occurred in each subject and applied for inducing diplopia in each direction of vergence. Using the TETRAX biofeedback system, the fall risk index (FI) was measured at each test condition and compared with that without prism effect. Also, the difference of FI depending on the amount of breakpoint in horizontal vergence was investigated. Results: FI was increased significantly when involved FC and VV for maintaining binocular single vision, but, FI decreased to the state without prism effect while diplopia is occurred. FI showed a higher tendency in the group with low BO break point. Conclusions: Even if binocular single vision was maintained, the visual state intervened FC and VV was analyzed as a factor that more increasing the risk of falling than the diplopia state.