School of Health Studies, University of Bradford, Bradford, West Yorkshire, United Kingdom.
PLoS One. 2013 May 22;8(5):e63351. doi: 10.1371/journal.pone.0063351. Print 2013.
Large changes in spectacle prescription can increase falls risk in older people. We investigated the effect of induced astigmatism (a common cause of distorted or blurred vision in older people) on locomotor stepping patterns to determine whether the orientation of astigmatic changes could have differential effects on gait safety when negotiating steps and stairs.
10 older adults (mean age 76.0±6.4 years) walked up to and stepped onto a raised block whilst wearing their spectacle prescription and when blurred with ±3.00D cylinders at axes 45°, 90°, 135° and 180°. Gait measurements included foot placement before the block, toe clearance over the block edge and foot placement on the block.
Induced astigmatism with axes at 90°, providing magnification in the horizontal meridian only, caused no change in stepping pattern. Induced astigmatism with axes at 180° caused foot placement changes in the anterior or posterior direction according to whether magnification was positive or negative in the vertical meridian (block perceived higher or lower respectively). Induced astigmatism with axes oblique at 45° and 135° (causing the block to be perceived as a parallelogram sloping downwards either to the right or left) caused gait changes in the anterior and posterior, vertical and lateral directions. Changes in lateral foot placement appeared to be an attempt to maintain constant foot clearance levels over the block edge by stepping over the perceived 'lower' side of the 'sloping' block.
Astigmatic changes with oblique axes had the greatest effect on gait. Clinicians, including optometrists, physiotherapists, occupational therapists and nurses should counsel older patients about the effects of astigmatism on gait safety. Furthermore, partial prescribing of astigmatic corrections should be considered to reduce the risk of falling.
眼镜处方的大幅变化会增加老年人跌倒的风险。我们研究了诱发散光（老年人视力扭曲或模糊的常见原因）对行走步态模式的影响，以确定散光变化的方向在上下楼梯时对步态安全是否有不同的影响。
10 名老年人（平均年龄 76.0±6.4 岁）在佩戴眼镜和佩戴±3.00D 圆柱镜（轴位分别为 45°、90°、135°和 180°）时，走到并踏上一个凸起的木块。步态测量包括木块前足部的放置位置、脚趾越过木块边缘的净空高度和足部在木块上的放置位置。
90°轴位的诱发散光导致水平子午线仅出现放大，对行走模式没有影响。180°轴位的诱发散光导致足部前后方向的放置位置发生变化，这取决于垂直子午线中的放大是正还是负（分别认为木块更高或更低）。45°和 135°斜轴位的诱发散光（导致木块被感知为一个向下倾斜的平行四边形，向左或向右倾斜）导致前后、垂直和侧向方向的步态变化。侧向足部放置位置的变化似乎是试图通过跨过感知到的“较低”的“倾斜”木块的一侧来保持越过木块边缘的恒定净空高度。
斜轴位的散光变化对步态影响最大。临床医生，包括验光师、物理治疗师、职业治疗师和护士，应告知老年患者散光对步态安全的影响。此外，应考虑部分矫正散光，以降低跌倒风险。
