Applied Vision Research Centre, The Henry Wellcome Laboratories for Vision Sciences, School of Health Sciences, City University London, London, United Kingdom.
Invest Ophthalmol Vis Sci. 2013 Sep 9;54(9):6093-103. doi: 10.1167/iovs.13-12119.
It is challenging to separate the effects of normal aging of the retina and visual pathways independently from optical factors, decreased retinal illuminance, and early stage disease. This study determined limits to describe the effect of light level on normal, age-related changes in monocular and binocular functional contrast sensitivity.
We recruited 95 participants aged 20 to 85 years. Contrast thresholds for correct orientation discrimination of the gap in a Landolt C optotype were measured using a 4-alternative, forced-choice (4AFC) procedure at screen luminances from 34 to 0.12 cd/m(2) at the fovea and parafovea (0° and ±4°). Pupil size was measured continuously. The Health of the Retina index (HRindex) was computed to capture the loss of contrast sensitivity with decreasing light level. Participants were excluded if they exhibited performance outside the normal limits of interocular differences or HRindex values, or signs of ocular disease.
Parafoveal contrast thresholds showed a steeper decline and higher correlation with age at the parafovea than the fovea. Of participants with clinical signs of ocular disease, 83% had HRindex values outside the normal limits. Binocular summation of contrast signals declined with age, independent of interocular differences.
The HRindex worsens more rapidly with age at the parafovea, consistent with histologic findings of rod loss and its link to age-related degenerative disease of the retina. The HRindex and interocular differences could be used to screen for and separate the earliest stages of subclinical disease from changes caused by normal aging.
独立于光学因素、视网膜照度降低和早期疾病，分离视网膜和视觉通路的正常老化效应具有挑战性。本研究旨在确定描述光水平对单眼和双眼功能对比敏感度的正常、年龄相关性变化的影响的极限。
我们招募了 95 名年龄在 20 至 85 岁之间的参与者。使用 4 种替代、强制选择（4AFC）程序，在屏幕亮度为 34 至 0.12 cd/m²的黄斑和旁黄斑（0°和±4°）处测量兰多尔特 C 视标缺口正确定向分辨的对比度阈值。连续测量瞳孔大小。计算健康视网膜指数（HRindex）以捕捉随着光水平降低对比度敏感度的损失。如果参与者的双眼差异或 HRindex 值超出正常范围，或出现眼部疾病迹象，则将其排除在外。
旁黄斑对比度阈值在旁黄斑处的下降更陡峭，与年龄的相关性高于黄斑处。在有眼部疾病临床体征的参与者中，83%的 HRindex 值超出正常范围。对比度信号的双眼总和随年龄的增长而下降，与双眼差异无关。
HRindex 在旁黄斑处随年龄的增长而迅速恶化，与组织学上发现的视杆细胞丧失及其与视网膜年龄相关性退行性疾病的关系一致。HRindex 和双眼差异可用于筛选和分离亚临床疾病的早期阶段与正常衰老引起的变化。
