THE DESIGN OF A NEW LETTER CHART FOR MEASURING CONTRAST SENSITIVITY
THE DESIGN OF A NEW LETTER CHART FOR MEASURING CONTRAST SENSITIVITY
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发表时间：
1988
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通讯作者：
D. Pelli;J. Robson;A. Wilkins
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作者：
D. Pelli;J. Robson;A. Wilkins
Summary-I。对比敏感度评估方法的考虑导致结论，对于临床试验，字母比光栅更合适。2. 文中描述了一个字母图表，其中字母的对比度减小，但尺寸没有减小。这些字母按三个字母一组排列；连续组的对比度降低IfJ2的一个因素，从一个非常高的对比度下降到低于正常观察者的阈值。受试者的阈值被认为是一组中至少两个字母被正确报道的最低对比度。3. 一个观察者和图表测试过程的数学模型已经被用来预测测试分数的准确性和可重复性如何依赖于图表和观察者的参数。这表明，如果通过标准严格，要求每组所有字母都正确报告，即使是低概率的误报超阈值字母也会严重影响考试成绩，但如果通过标准不严格，则影响不大。这种通过标准的影响可以解释鲁宾的克林。视觉科学2，第2期。I(1987)]发现使用宽松标准的新测试具有优异的重测信度，远高于Ginsburg [Am。j . Optom。杂志。[Opt. 61,403-407(1984)]具有严格标准的图表。
Summary-I. A consideration of methods for assessing contrast sensitivity leads to the conclusion that, for a clinical test, letters are more suitable than gratings. 2. A letter chart isdescribed in which letters decrease in contrast but not in size. The letters are arranged in groups of three; successive groups decrease in contrast by a factor of IfJ2 from a very high contrast down to a contrast below the threshold of normal observers. A subject's threshold is taken to be the lowest contrast for which at least two letters in a group are correctly reported. 3. A mathematical model of the observer and the chart-testing procedure has been used to predict how the accuracy and repeatability of the test score depend on the parameters of the chart and observer. This reveals that even a low probability of misreporting suprathreshold letters will seriously bias the test score if the passing criterion is strict, requiring correct report of all letters in each group, but will have little effect if the passing criterion is less strict. This effect of the passing criterion may explain Rubin's [Clin. Vision Sci. 2, No. I (1987)]finding that the new test, which uses a lenient criterion, has excellent test-retest reliability, much higher than the Ginsburg [Am. J. Optom. Physiol. Opt. 61,403-407 (1984)] chart with its strict criterion.