Pyne Jeffrey D, Genovese Katia, Casaletto Luciana, Vande Geest Jonathan P
J Biomech Eng. 2014 Feb;136(2):021002. doi: 10.1115/1.4026224.
Optic nerve head (ONH) deformations may be involved in the onset or further development of glaucoma, including in patients with relatively normal intraocular pressures (IOPs). Characterizing posterior scleral deformations over physiological pressures may provide a better understanding of how changes in IOP lead to changes in the mechanical environment of the ONH and possibly retinal ganglion cell death. Pressure inflation measurement test protocols are commonly used to measure deformation of the peripapillary sclera with full-field noncontact optical methods. The purpose of this work was to develop and validate a new sequential 3D digital image correlation (S-DIC) approach for quantification of posterior scleral pressure induced deformation that improves z (in-depth) resolution of the DIC measurement without losing in-plane sensitivity, while also being able to contour and map deformations of the complex-shaped ONH. Our approach combines two orthogonal axes of parallax with standard 3D DIC methods using a single high-resolution camera. The enhanced capabilities of S-DIC with respect to standard 3D DIC has been demonstrated by carrying out a complete benchmark for shape, deformation, and strain measurement on an object of known complex geometry. Our S-DIC method provided a reconstruction accuracy of 0.17% and an uncertainty in z-position measurement of 8 μm. The developed methodology has also been applied to a human posterior scleral shell, including the full peripapillary sclera and optic nerve. The relatively inexpensive S-DIC approach may provide new information on the biomechanical deformations of the optic nerve head and, thus, the death of retinal ganglion cells in primary open angle glaucoma.
视神经乳头（ONH）变形可能参与青光眼的发病或进一步发展，包括眼压（IOP）相对正常的患者。表征生理压力下的后巩膜变形可能有助于更好地理解眼压变化如何导致视神经乳头机械环境的改变以及可能的视网膜神经节细胞死亡。压力充气测量测试方案通常用于通过全场非接触光学方法测量视乳头周围巩膜的变形。这项工作的目的是开发并验证一种新的顺序三维数字图像相关（S-DIC）方法，用于量化后巩膜压力诱导的变形，该方法可提高DIC测量的z（深度）分辨率而不损失面内灵敏度，同时还能够勾勒并绘制复杂形状的视神经乳头的变形。我们的方法使用单个高分辨率相机将两个正交视差轴与标准三维DIC方法相结合。通过对已知复杂几何形状的物体进行形状测量、变形测量和应变测量的完整基准测试，已证明S-DIC相对于标准三维DIC具有增强的功能。我们的S-DIC方法提供了0.17%的重建精度和8μm的z位置测量不确定度。所开发的方法也已应用于人类后巩膜壳，包括整个视乳头周围巩膜和视神经。相对廉价的S-DIC方法可能会提供有关原发性开角型青光眼视神经乳头生物力学变形以及视网膜神经节细胞死亡的新信息。
