Bradford School of Optometry and Vision Science, University of Bradford, Bradford, United Kingdom.
Invest Ophthalmol Vis Sci. 2010 Feb;51(2):718-22. doi: 10.1167/iovs.09-4250. Epub 2009 Sep 24.
A recent study suggested that updated spectacles could increase fall rate in frail older people. The authors hypothesized that the increased risk may be due to changes in spectacle magnification. The present study was conducted to assess the effects of spectacle magnification on step negotiation.
Adaptive gait and visual function were measured in 10 older adults (mean age, 77.1 +/- 4.3 years) with the participants' optimal refractive correction and when blurred with +1.00, +2.00, -1.00, and -2.00 DS lenses. Adaptive gait measurements for the leading and trailing foot included foot position before the step, toe clearance of the step edge, and foot position on the step. Vision measurements included visual acuity, contrast sensitivity, and stereoacuity.
The blur lenses led to equal decrements in visual acuity and stereoacuity for the +1.00 and -1.00 DS and the +2.00 and -2.00 DS lenses. However, they had very different effects on step negotiation compared with the optimal correction. Positive-blur lenses led to an increased distance of the feet from the step, increased vertical toe clearance and reduced distance of the leading heel position on the step. Negative lenses led to the opposite of these changes.
The step negotiation changes did not mirror the effects of blur on vision, but were driven by the magnification changes of the lenses. Steps appear closer and larger with positive lenses and farther away and smaller with negative ones. Magnification is a likely explanation of the mobility problems some older adults have with updated spectacles and after cataract surgery.
最近的一项研究表明，更新的眼镜可能会增加体弱老年人的跌倒率。作者假设，这种风险增加可能是由于眼镜放大倍数的变化。本研究旨在评估眼镜放大倍数对步幅协商的影响。
对 10 名年龄在 77.1±4.3 岁的老年人进行适应性步态和视觉功能测量，参与者的最佳屈光矫正和模糊时 +1.00、+2.00、-1.00 和-2.00 DS 镜片。领先和尾随脚的适应性步态测量包括步前脚的位置、步边缘的脚趾间隙和步上的脚的位置。视觉测量包括视力、对比敏感度和立体视锐度。
模糊镜片导致 +1.00 和-1.00 DS 以及+2.00 和-2.00 DS 镜片的视力和立体视锐度相等下降。然而，与最佳矫正相比，它们对步幅协商有非常不同的影响。正模糊镜片导致脚与台阶的距离增加，垂直脚趾间隙增加，领先脚跟在台阶上的位置距离减小。负透镜导致相反的变化。
步幅协商的变化与模糊对视力的影响不相符，而是由镜片的放大倍数变化驱动的。正透镜使台阶看起来更近更大，而负透镜则使台阶看起来更远更小。放大倍数可能是一些老年人在更新眼镜和白内障手术后出现移动问题的原因。
