Sektion Funktionelle Sehforschung, Univ.-Augenklinik, Killianstr. 5, 79106 Freiburg, Germany.
Graefes Arch Clin Exp Ophthalmol. 2010 Mar;248(3):389-94. doi: 10.1007/s00417-009-1268-2.
A high reproducibility of visual acuity estimates is important when monitoring disease progression or treatment success. One factor that may affect the result of an acuity measurement is the duration of optotype presentation. For times below 1 s, previous studies have convincingly shown that acuity estimates increase with presentation duration. For durations above 1 s, the situation is less clear.
We have reassessed this issue using the Freiburg Visual Acuity Test with normal subjects. Presentation durations of 0.1 s, 1 s, and 10 s were assessed.
Confirming previous findings, in all subjects acuity estimates in the 1-s condition were higher than those in the 0.1-s condition, on average nearly by a factor of 2, equivalent to 3 lines. However, in 12 out of 14 subjects, acuity estimates increased further with a presentation duration of 10 s, on average by 23% (P=0.002), or roughly 1 line. Test-retest variability improved by 49% (P=0.003). These findings can be explained by a simple statistical model of acuity fluctuations. Cognitive processing may also be a relevant factor. Interestingly, most observers subjectively felt that they could perceive the optotypes best in the 1-s condition.
The results highlight the importance of standardizing presentation durations when high reproducibility is required.
当监测疾病进展或治疗效果时，视力估计的高重复性非常重要。可能影响视力测量结果的一个因素是视标呈现的持续时间。对于 1 秒以下的时间，以前的研究已经令人信服地表明，视力估计值随着呈现时间的延长而增加。对于 1 秒以上的持续时间，情况就不那么清楚了。
我们使用弗莱堡视觉 acuity 测试（Freiburg Visual Acuity Test）重新评估了这个问题，研究对象为正常受试者。评估了 0.1 秒、1 秒和 10 秒的呈现持续时间。
与之前的发现一致，在所有受试者中，1 秒条件下的视力估计值均高于 0.1 秒条件下的，平均接近 2 倍，相当于 3 行。然而，在 14 名受试者中有 12 名，10 秒呈现持续时间的视力估计值进一步增加，平均增加 23%（P=0.002），或大致增加 1 行。测试-重测的可变性提高了 49%（P=0.003）。这些发现可以用视力波动的简单统计模型来解释。认知处理也可能是一个相关因素。有趣的是，大多数观察者主观上感觉他们在 1 秒的条件下可以最好地感知视标。
这些结果强调了在需要高重复性时标准化呈现持续时间的重要性。
