基于Scheimpflug高速摄像技术的在体角膜生物力学测量方法的建立与应用研究

Cornea belongs to the biological viscoelastic tissue. Its biomechanical property is the basis of the normal structural form and the refractive function of the eye. Currently, there are only a few commercial instruments for corneal biomechanical measurement in clinic. But the results of these measurements are not classical mechanical parameters and with a poor efficiency diagnosis for corneal ectasia diseases. Our previous study found that ultra-high speed Scheimpflug camera can record the information on corneal deformation in real time. Using the self-developed system, the corneal boundary curves were extracted. For the preliminary work, cooperated with the Hong Kong Polytechnic University, the ultra-high speed Scheimpflug camera based air jet indentation technology (SJIT) for measuring the biomechanical properties of cornea were designed and built. This study intends to measure the air jet force and distribution of SJIT and combined with the corneal deformation process to design several new biomechanical parameters, which based on the model of classical mechanics. In vitro experiments were used to verify the feasibility and effectiveness of the new system, and analyze the influence mechanism of ocular characteristics to the new parameters. In vivo clinical experiments were used to study the repeatability and reproducibility of the new parameters and analyze the diagnostic efficiency in keratoconus. The successful implementation of this project will establish a new method of in vivo corneal biomechanical measurement and put forward the biomechanical parameters, that accord with the concept of classical mechanics, for the first time. This project also will lay a solid foundation for clinical application.

角膜属于生物粘弹性组织器官，其生物力学特性是保持眼正常形态与屈光功能的结构基础。目前临床中仅有的在体角膜生物力学测量设备，测量结果均非经典力学概念参数，且对角膜扩张类疾病的诊断效率欠佳。前期研究我们发现Scheimpflug高速像机能够实时记录角膜形变过程，并应用自主研发的角膜边界识别系统，提取出形变过程中的角膜边界曲线。申请者与香港理工大学团队合作已初步搭建Scheimpflug高速摄像联合气冲印压系统样机。本课题拟通过测量新系统的气脉冲强度和分布特征，结合角膜形变过程，构建经典力学概念的生物力学新参数。通过离体实验验证新方法的可行性和有效性；观察眼部特性的改变对新参数的影响效果，分析其作用机制。通过临床实验检验新参数的重复性和一致性；分析新参数对圆锥角膜的诊断效率。本项目的顺利实施将建立一种新的生物力学在体测量方法，并首次提出符合经典生物力学概念的新参数，为临床应用奠定坚实基础。

本项目建立了基于Scheimpflug高速摄像技术在体测量角膜生物力学的方法，获得了STSC，Aabsorbed及角膜弹性模量等符合经典力学概念的新参数；通过离体对比角膜单轴拉伸实验及有限元方法对新参数的可行性和有效性进行了验证，结果显示新参数可以有效地反应角膜的生物力学特性；对离体眼球进行测试，分析了眼内压、角膜厚度、角膜刚度、眼外肌等对新参数的影响。角膜弹性模量受眼内压、角膜刚度的影响更显著，受离体环境（眼外肌）的影响较小。即当保持眼压和角膜正常的形态时，在体与离体环境测试得到的弹性模量值没有明显差异。对正常受试者进行测试获得了新参数的正常取值范围。对圆锥角膜患者及屈光手术患者术前和术后进行测试，初步获得新参数对圆锥角膜诊断效率和在屈光手术筛查中的价值。