Nonlinear Optical Macroscopic Assessment of 3-D Corneal Collagen Organization and Axial Biomechanics
Nonlinear Optical Macroscopic Assessment of 3-D Corneal Collagen Organization and Axial Biomechanics
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DOI：
10.1167/iovs.11-8070
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发表时间：
2011-11-01
影响因子：
4.4
通讯作者：
Jester, James V.
中科院分区：
文献类型：
--
作者：
Winkler, Moritz;Chai, Dongyul;Jester, James V.
目的。使用非线性光学高分辨率宏观显微镜 (NLO-HRMac) 在三个维度上表征和量化人类角膜的胶原纤维（层状）组织，并将这些发现与通过角膜瓣压痕测试获得的机械数据相关联。方法。研究人员对来自 10 位捐赠者的 12 个角膜进行了研究。沿着垂直子午线从角膜缘到角膜缘（弧长，12毫米）切割来自五个供体眼睛的200μm厚的振动切片。来自这些部分的反向散射二次谐波生成 (SHG) NLO 信号被收集为一系列重叠的 3D 图像，这些图像连接起来形成单个 3D 马赛克（像素分辨率：横向 0.44 μm，轴向 2 μm）。通过确定分支点密度作为基质深度的函数来量化胶原纤维的缠绕。对另外七只眼睛的角膜瓣进行了机械测试。使用飞秒手术激光系统将角膜切割成三层（前层、中层和后层），并进行压痕测试以确定每层的弹性模量。 结果。 3D 重建揭示了前角膜中复杂的胶原纤维分支模式，纤维从前限制层（ALL，鲍曼层）延伸，与更深的纤维交织在一起并重新插入回 ALL，形成弓形弹簧状结构。测得的角膜前三分之一的分支点密度是后三分之一的四倍，并且随着距 ALL 距离的增加呈对数下降。压痕测试显示前基质的弹性模量增加了八倍。结论。层状缠绕的轴向梯度似乎与角膜有效弹性模量的轴向梯度相关，这表明胶原纤维缠绕和弓形弹簧结构的形成提供了类似于桥梁和大型结构中的横梁的结构支撑。未来的研究有必要确定径向和轴向结构机械异质性在控制角膜形状以及圆锥角膜、散光和其他屈光不正的发展中的作用。 （投资眼科可见科学。2011；52：8818-8827）DOI：10.1167/iovs.11-8070
PURPOSE. To characterize and quantify the collagen fiber (lamellar) organization of human corneas in three dimensions by using nonlinear optical high-resolution macroscopy (NLO-HRMac) and to correlate these findings with mechanical data obtained by indentation testing of corneal flaps.METHODS. Twelve corneas from 10 donors were studied. Vibratome sections, 200 mu m thick, from five donor eyes were cut along the vertical meridian from limbus to limbus (arc length, 12 mm). Backscattered second harmonic-generated (SHG) NLO signals from these sections were collected as a series of overlapping 3-D images, which were concatenated to form a single 3-D mosaic (pixel resolution: 0.44 mu m lateral, 2 mu m axial). Collagen fiber intertwining was quantified by determining branching point density as a function of stromal depth. Mechanical testing was performed on corneal flaps from seven additional eyes. Corneas were cut into three layers (anterior, middle, and posterior) using a femtosecond surgical laser system and underwent indentation testing to determine the elastic modulus for each layer.RESULTS. The 3-D reconstructions revealed complex collagen fiber branching patterns in the anterior cornea, with fibers extending from the anterior limiting lamina (ALL, Bowman's layer), intertwining with deeper fibers and reinserting back to the ALL, forming bow spring-like structures. Measured branching-point density was four times higher in the anterior third of the cornea than in the posterior third and decreased logarithmically with increasing distance from the ALL. Indentation testing showed an eightfold increase in elastic modulus in the anterior stroma.CONCLUSIONS. The axial gradient in lamellar intertwining appears to be associated with an axial gradient in the effective elastic modulus of the cornea, suggesting that collagen fiber intertwining and formation of bow spring-like structures provide structural support similar to cross-beams in bridges and large-scale structures. Future studies are necessary to determine the role of radial and axial structural-mechanical heterogeneity in controlling corneal shape and in the development of keratoconus, astigmatism, and other refractive errors. (Invest Ophthalmol Vis Sci. 2011;52:8818-8827) DOI:10.1167/iovs.11-8070