Mei Ming, Leat Susan J, Hovis Jeffery
School of Optometry, University of Waterloo, Waterloo, Canada.
Clin Exp Optom. 2007 Jul;90(4):272-81. doi: 10.1111/j.1444-0938.2007.00162.x.
The effects of age on contrast threshold are well known but little is known about its effect on supra-threshold contrast perception. This study examines supra-threshold contrast matching and the effects of age in naïve observers.
Two age groups (from 20 to 50 years with 14 subjects and 51 years and older with 15 subjects) participated in the study. Contrast threshold and supra-threshold contrast matching up to 8.53 cycles per degree were measured.
Both age groups demonstrated some degree of contrast constancy at medium and higher contrasts but this was not perfect even at the highest contrast tested (55.9 per cent). There was no overall effect of age on supra-threshold contrast matching (p = 0.086) but there was an interaction between age and spatial frequency (p < 0.001). The plots of matched contrast against standard contrast showed that for some spatial frequencies, the slope was significantly different from unity, indicating a gain in the visual system for supra-threshold perception. This was still true when corrected for threshold differences.
Contrast constancy exists in a larger group of naïve subjects of different ages but does not perfectly compensate for the differences in thresholds. The results are discussed in terms of the currently proposed models of contrast perception.
年龄对对比度阈值的影响已为人熟知，但关于其对超阈值对比度感知的影响却知之甚少。本研究考察了超阈值对比度匹配以及年龄对未经训练的观察者的影响。
两个年龄组（20至50岁，14名受试者；51岁及以上，15名受试者）参与了该研究。测量了对比度阈值和高达每度8.53周的超阈值对比度匹配。
两个年龄组在中等和较高对比度下均表现出一定程度的对比度恒常性，但即使在测试的最高对比度（55.9%）下也并不完美。年龄对超阈值对比度匹配没有总体影响（p = 0.086），但年龄与空间频率之间存在交互作用（p < 0.001）。匹配对比度与标准对比度的关系图表明，对于某些空间频率，斜率显著不同于1，表明视觉系统在超阈值感知方面存在增益。在校正阈值差异后，情况依然如此。
在不同年龄的大量未经训练的受试者中存在对比度恒常性，但不能完全补偿阈值差异。根据当前提出的对比度感知模型对结果进行了讨论。
