Tahir Humza J, Rodrigo-Diaz Elena, Parry Neil R A, Kelly Jeremiah M F, Carden David, Murray Ian J
Faculty of Life Sciences, University of Manchester, Manchester, UK.
Faculty of Life Sciences, University of Manchester, Manchester, UK.
Exp Eye Res. 2017 Feb;155:47-53. doi: 10.1016/j.exer.2016.11.016. Epub 2016 Nov 24.
The rate of rod sensitivity recovery following a photobleach is a basic measure of the integrity of the outer retina. Rods are selectively impaired in aging and many disorders of the retina, notably Age-Related Macular Degeneration (AMD). It is not known for certain whether the age-related deficit is a pan-retinal effect or if there are localised regions of impaired rod function. To address this important issue a dual arc stimulus was developed that samples sensitivity recovery in two retinal locations.
Arc-shaped stimuli were presented on a black CRT screen at two locations, in the inferior visual field. Following a bleach, which was localised to the stimuli, recovery of sensitivity was measured using a modified method of adjustment technique. Neutral density filters were used to extend the luminance range of the CRT. Sensitivity recovery functions were fitted by non-linear regression to a seven-parameter model.
Pairs of sensitivity recovery functions were generated from the stimuli. The cone phases of these functions were identical. The slopes of the S2 sections of the curves were steeper for the outer stimuli for both young (p < 0.001) and older (p = 0.003) observers. The difference between the two was the same for the two groups. The α point was reached slightly earlier for the young observers and with the outer stimulus but neither of these effects reached statistical significance. The β point occurred earlier for the outer stimuli and this effect was statistically significant only for the older group.
The method places minimal demands on observers. The fact that rod sensitivity recovery is slowed in the older normal eye to the same extent in the two locations suggests that this deficit may be uniform across the retina. As there are localised losses in scotopic function in AMD, the technique is ideally suited to distinguishing impaired recovery dynamics due to normal ageing from those caused by disease.
光漂白后视杆细胞敏感性恢复速率是视网膜外层完整性的一项基本指标。视杆细胞在衰老及许多视网膜疾病（尤其是年龄相关性黄斑变性，AMD）中会选择性受损。目前尚不确定年龄相关的缺陷是全视网膜效应，还是存在视杆细胞功能受损的局部区域。为解决这一重要问题，开发了一种双弧形刺激，用于在两个视网膜位置采样敏感性恢复情况。
在黑色阴极射线管（CRT）屏幕的两个位置（在下视野）呈现弧形刺激。在对刺激区域进行局部漂白后，使用改良的调整技术方法测量敏感性恢复情况。使用中性密度滤光片扩展CRT的亮度范围。通过非线性回归将敏感性恢复函数拟合到一个七参数模型。
从刺激中生成了成对的敏感性恢复函数。这些函数的视锥细胞阶段是相同的。对于年轻（p < 0.001）和年长（p = 0.003）观察者，曲线S2部分的斜率在外层刺激时更陡。两组中两者之间的差异相同。年轻观察者在外层刺激时α点稍早达到，但这两种效应均未达到统计学显著性。β点在外层刺激时出现得更早，且仅在年长组中这种效应具有统计学显著性。
该方法对观察者的要求极低。正常老年眼中视杆细胞敏感性恢复在两个位置同样减慢，这一事实表明这种缺陷可能在整个视网膜上是一致的。由于AMD存在暗视功能的局部丧失，该技术非常适合区分正常衰老导致的恢复动力学受损与疾病导致的恢复动力学受损。
