Pardhan S, Gilchrist J, Elliott D B, Beh G K
Department of Optometry, University of Bradford, U.K.
Vision Res. 1996 Jun;36(11):1641-8. doi: 10.1016/0042-6989(95)00214-6.
Contrast detection in different levels of external visual noise allows a given loss in contrast sensitivity to be attributed to either an increase in the internal noise of the visual system, a decrease in sampling efficiency, or both. Sampling efficiency indicates how effectively the available stimulus information is utilized by the visual system. The aim of this study is to investigate the effect of normal ageing on sampling efficiency and internal noise. Contrast thresholds for sine-wave gratings of 6 c/deg were measured in the presence of four (including zero) levels of externally added visual noise in young and older healthy observers. Results showed that sampling efficiencies were significantly lower for the older group compared to the younger, while the internal noise showed no significant change. The implications of the data for the relative contribution of the optical and neural systems on visual function loss with ageing are discussed. Our results suggest that the neural system plays a major role in the loss of contrast sensitivity with ageing in normal, healthy eyes.
在不同水平的外部视觉噪声中进行对比度检测，可以将对比度敏感度的给定损失归因于视觉系统内部噪声的增加、采样效率的降低或两者兼而有之。采样效率表明视觉系统利用可用刺激信息的有效程度。本研究的目的是调查正常衰老对采样效率和内部噪声的影响。在年轻和年长的健康观察者中，在存在四种（包括零）水平的外部添加视觉噪声的情况下，测量了6 c/deg正弦波光栅的对比度阈值。结果表明，与年轻组相比，年长组的采样效率显著更低，而内部噪声没有显著变化。讨论了这些数据对于光学和神经系统对衰老导致的视觉功能丧失的相对贡献的意义。我们的结果表明，在正常健康眼睛中，神经系统在衰老导致的对比度敏感度丧失中起主要作用。
