An investigation was carried out with the aim of reconstructing the gradient index (GRIN) profile of human crystalline lenses ex-vivo using optical coherence tomography (OCT) imaging with an optimization technique and to study the dependence of the GRIN profile with age. Cross-sectional images of nine isolated human crystalline lenses with ages ranging from 6 to 72 (post-mortem time 1 to 4 days) were obtained using a custom-made OCT system. Lenses were extracted from whole cadaver globes and placed in a measurement chamber filled with preservation medium (DMEM). Lenses were imaged with the anterior surface up and then flipped over and imaged again, to obtain posterior lens surface profiles both undistorted and distorted by the refraction through the anterior crystalline lens and GRIN. The GRIN distribution of the lens was described with three variables by means of power function, with variables being the nucleus and surface index, and a power coefficient that describes the decay of the refractive index from the nucleus to the surface. An optimization method was used to search for the parameters that produced the best match of the distorted posterior surface. The distorted surface was simulated with accuracy around the resolution of the OCT system (under 15 µm). The reconstructed refractive index values ranged from 1.356 to 1.388 for the surface, and from 1.396 to 1.434 for the nucleus. The power coefficient ranged between 3 and 18. The power coefficient increased significantly with age, at a rate of 0.24 per year. Optical coherence tomography allowed optical, non-invasive measurement of the 2D gradient index profile of the isolated human crystalline lens ex vivo. The age-dependent variation of the changes is consistent with previous data using magnetic resonance imaging, and the progressive formation of a refractive index plateau.

中文翻译：

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人晶状体中梯度折射率分布的年龄相关变化

进行了一项调查，目的是使用光学相干断层扫描 (OCT) 成像和优化技术重建离体人晶状体的梯度指数 (GRIN) 剖面，并研究 GRIN 剖面与年龄的依赖性。使用定制的 OCT 系统获得了 9 个年龄在 6 到 72 岁之间（验尸时间为 1 到 4 天）的孤立人类晶状体的横截面图像。从整个尸体球体中提取镜片并放置在充满保存介质 (DMEM) 的测量室中。镜片前表面向上成像，然后翻转并再次成像，以获得未失真和因通过前晶状体和 GRIN 折射而失真的镜片后表面轮廓。透镜的 GRIN 分布通过功率函数用三个变量来描述，变量是核和表面指数，以及描述折射率从核到表面衰减的功率系数。使用优化方法来搜索产生失真后表面的最佳匹配的参数。扭曲的表面以围绕 OCT 系统分辨率（15 µm 以下）的精度进行模拟。表面重建的折射率值范围为 1.356 至 1.388，核的重建折射率值为 1.396 至 1.434。功率系数在 3 到 18 之间。功率系数随着年龄的增长显着增加，以每年 0.24 的速度增加。光学相干断层扫描允许光学，离体人晶状体二维梯度指数分布的非侵入性测量。这些变化的年龄相关变化与先前使用磁共振成像的数据以及折射率平台的逐渐形成一致。