Sektion Funktionelle Sehforschung, Univ.-Augenklinik, Freiburg, Germany.
Ophthalmic Physiol Opt. 2011 Nov;31(6):625-31. doi: 10.1111/j.1475-1313.2011.00857.x. Epub 2011 Jul 14.
Artificial degradation of vision by inducing dioptric blur is frequently used for evaluating diagnostic equipment. However, the use of lenses is prone to errors as it is adversely affected by eyelid squinting, pupil size, and imprecise lens position. The alternative is a degradation of the stimuli themselves based on a Fourier-optical mathematical model. With this, however, perceptual effects such as 'simultaneous blur' induced by the surround may affect acuity. We tested whether both methods, lens induced defocus and mathematical stimulus degradation, yield concordant results.
We compared both methods in normal subjects, measuring Landolt C acuity at five different levels of defocus from 0 to 8 dioptres. The pupil size was determined individually, chromatic aberrations were avoided by using a monochromatic approach, and a correction for spectacle magnification was included. Otherwise, the experimental design was kept deliberately simple to remain comparable to typical applications.
With the major sources of error associated with the use of lenses being accounted for, both methods yield similar mean results with differences in acuity ranging from <0.001 to 0.054 logMAR (0.2-13%).
Using mathematically simulated defocus is a viable option if both reasonable accuracy and ease of use are required. The fact that the application of the mathematical model only blurs the stimulus itself, but not the surrounding environment, does not appear to be detrimental to the method.
通过诱导屈光度模糊来人为降低视力通常用于评估诊断设备。然而，由于眼睑眯眼、瞳孔大小和透镜位置不精确等因素的影响，使用透镜容易产生误差。另一种方法是基于傅里叶光学数学模型来降低刺激本身的质量。然而，这种方法可能会产生“同时模糊”等感知效应，从而影响视力敏锐度。我们测试了这两种方法，即透镜引起的散焦和数学刺激退化，是否会产生一致的结果。
我们在正常受试者中比较了这两种方法，在 0 到 8 屈光度的五个不同散焦水平下测量了 Landolt C 视力。个别确定瞳孔大小，避免使用单色方法产生色差，并包括眼镜放大率的校正。否则，实验设计故意保持简单，以保持与典型应用的可比性。
在考虑了与使用透镜相关的主要误差源后，这两种方法得出了相似的平均结果，视力差异范围从<0.001 到 0.054 logMAR（0.2-13%）。
如果需要合理的准确性和易用性，那么使用数学模拟的散焦是一种可行的选择。应用数学模型只会使刺激本身模糊，而不会使周围环境模糊，这似乎对该方法没有不利影响。
