Vale Anna, Scally Andy, Buckley John G, Elliott David B
Vision and Mobility Research Laboratory, School of Health Studies, University of Bradford, Bradford, UK.
Ophthalmic Physiol Opt. 2008 Mar;28(2):135-42. doi: 10.1111/j.1475-1313.2008.00543.x.
Falls in the elderly are a major cause of mortality and morbidity. Elderly people with visual impairment have been found to be at increased risk of falling, with poor visual acuity in one eye causing greater risk than poor binocular visual acuity. The present study investigated whether monocular refractive blur, at a level typically used for monovision correction, would significantly reduce stereoacuity and consequently affect gait parameters when negotiating a raised surface. Fourteen healthy subjects (25.8 +/- 5.6 years) walked up to and on to a raised surface, under four visual conditions; binocular, +2DS blur over their non-dominant eye, +2DS blur over their dominant eye and with their dominant eye occluded. Analysis focussed on foot positioning and toe clearance parameters. Monocular blur had no effect on binocular acuity, but caused a small decline in binocular contrast sensitivity and a large decline in stereoacuity (p < 0.01). Vertical toe clearance increased under monocular blur or occlusion (p < 0.01) with a significantly greater increase under blur of the dominant eye compared with blur of the non-dominant eye (p < 0.01). Increase in toe clearance was facilitated by increasing maximum toe elevation (p < 0.01). Findings indicate that monocular blur at a level typically used for monovision correction significantly reduced stereoacuity and consequently the ability to accurately perceive the height and position of a raised surface placed within the travel path. These findings may help explain why elderly individuals with poor visual acuity in one eye have been found to have an increased risk of falling.
老年人跌倒乃是导致死亡和发病的主要原因。研究发现，视力受损的老年人跌倒风险增加，单眼视力不佳比双眼视力不佳造成的风险更大。本研究调查了单眼屈光性模糊（处于通常用于单眼视力矫正的水平）在通过一个升高表面时是否会显著降低立体视敏度，进而影响步态参数。14名健康受试者（25.8±5.6岁）在四种视觉条件下走上并走过一个升高表面；双眼视觉、非优势眼上加+2DS模糊、优势眼上加+2DS模糊以及优势眼被遮挡。分析重点在于足部定位和脚趾间隙参数。单眼模糊对双眼视力没有影响，但导致双眼对比敏感度略有下降，立体视敏度大幅下降（p<0.01）。单眼模糊或遮挡时垂直脚趾间隙增加（p<0.01），与非优势眼模糊相比，优势眼模糊时垂直脚趾间隙增加显著更大（p<0.01）。最大脚趾抬高增加有助于脚趾间隙增加（p<0.01）。研究结果表明，处于通常用于单眼视力矫正水平的单眼模糊会显著降低立体视敏度，从而降低准确感知行进路径内升高表面高度和位置的能力。这些发现可能有助于解释为何已发现单眼视力不佳的老年人跌倒风险增加。
