VanNasdale Dean A, Elsner Ann E, Hobbs Timothy, Burns Stephen A
Indiana University, School of Optometry, Bloomington 47405,USA.
Vision Res. 2011 Nov;51(21-22):2263-72. doi: 10.1016/j.visres.2011.08.017. Epub 2011 Aug 27.
This study quantified normal age-related changes to the photoreceptor axons in the central macula using the birefringent properties of the Henle fiber layer. A scanning laser polarimeter was used to acquire 15° × 15° macular images in 120 clinically normal subjects, ranging in age from the third decade to the eighth. Raw image data of the macular cross were used to compute phase retardation maps associated with Henle fiber layer. Annular regions of interest ranging from 0.25° to 3° eccentricity and centered on the fovea were used to generate intensity profiles from the phase retardation data, which were then analyzed using sine curve fitting and Fast Fourier Transform (FFT). The amplitude of a 2f sine curve was used as a measure of macular phase retardation magnitude. For FFT analysis, the 2f amplitude, as well as the 4f, were normalized by the remaining FFT components. The amplitude component of the 2f curve fit and the normalized 2f FFT component decreased as a function of age, while the eccentricity of the maximum value for the normalized 2f FFT component increased. The phase retardation changes in the central macula indicate structural alterations in the cone photoreceptor axons near the fovea as a function of age. These changes result in either fewer cone photoreceptors in the central macula, or a change in the orientation of their axons. This large sample size demonstrates systematic changes to the central cone photoreceptor morphology using scanning laser polarimetry.
本研究利用Henle纤维层的双折射特性，对中央黄斑区光感受器轴突与年龄相关的正常变化进行了量化。使用扫描激光偏振仪在120名临床正常受试者中采集15°×15°的黄斑图像，受试者年龄范围从三十多岁到八十岁。黄斑十字的原始图像数据用于计算与Henle纤维层相关的相位延迟图。以中央凹为中心、偏心率范围从0.25°至3°的环形感兴趣区域用于从相位延迟数据生成强度分布图，然后使用正弦曲线拟合和快速傅里叶变换（FFT）进行分析。2f正弦曲线的振幅用作黄斑相位延迟幅度的度量。对于FFT分析，2f振幅以及4f振幅通过其余FFT分量进行归一化。2f曲线拟合的振幅分量和归一化的2f FFT分量随年龄增长而降低，而归一化的2f FFT分量最大值的偏心率增加。中央黄斑区的相位延迟变化表明，中央凹附近视锥光感受器轴突的结构改变是年龄的函数。这些变化导致中央黄斑区视锥光感受器数量减少，或其轴突方向发生改变。如此大的样本量表明，使用扫描激光偏振仪可观察到中央视锥光感受器形态的系统性变化。
