Determination of Corneal Biomechanical Properties in vivo

尽管最近我们对角膜结构的理解和实验室中用于测试角膜组织的方法取得了进展，但仍然不可能在体内测量角膜特性。由于无法确定体内的基本生物力学特性（如超弹性，滞后和粘弹性），对我们优化治疗或预测其结果的能力产生了严重的不利影响，并且有必要依赖于体外获得的平均特性。它试图涵盖支持这项技术发展的研究需求，并解决阻碍这一领域取得进展的两个基本问题。这两个问题围绕着从整个角膜对机械作用的反应中提取材料的应力-应变行为。一旦这些障碍被消除，建立体内测量技术的途径就变得简单了。如果可以在体内测量角膜生物力学特性，就可以获得显著的潜在好处。这些例子包括更好地设计植入物，以恢复圆锥角膜患者的清晰视力，更好地规划屈光手术程序，目前导致1：7的患者出现意外像差，以及消除角膜硬度对眼内压测量的影响的能力，这是青光眼管理所需的。这些潜在的发展将意味着显着的好处，病人，医疗保健服务和医疗器械manufacturers.The研究开始与实验研究，以确定角膜和巩膜的超弹性，滞后和粘弹性的区域变化。该研究将使用3D数字成像的人眼球受到眼内压和外部压平力的循环，旨在解决眼睛生物力学知识的关键差距。建立生物力学特性的地图，将建立数值分析工具来体现这些地图，除了现有的知识，生物力学，地形和微观结构特征的人眼。这些工具将是定制的，将根据实验获得的眼部行为数据进行验证，然后使用它们开发概念技术来测量活体角膜生物力学。将评估基于接触和非接触方法的两种类型的属性测量技术。在这两种情况下，角膜对机械作用的反应与角膜应力-应变行为相关。这项工作将集中在关键的研究问题，并旨在正式的分析程序，以提取角膜的应力应变行为从其机械响应，并排除眼内压和角膜的几何参数的影响的结果。数值研究的结果将使用验证的概念原型进行评估，无论是在人类的眼球和志愿者在临床环境中的实验。测试的目的是验证数值结果，投光到机械作用下的眼变形的特点，并提供初步结果，这将是重要的，为未来的临床研究进行全面运作的设备prototype.Overall，该项目解决了一个具有挑战性的问题，影响了在眼科病人护理的几个领域的进展。它旨在克服使角膜特性的体内测量成为现实的主要障碍。该项目遵循一种系统的方法，在评估属性测量方法之前，生成有关眼部行为的必要知识并建立眼部机械响应的预测工具。通过本项目中产生的知识和理解，可以进行研发，将新技术体现在适合临床使用的医疗器械中。

Despite recent advances in our understanding of corneal structure and the methods used to test corneal tissue in the lab, it is still impossible to measure corneal properties in-vivo. The inability to determine the basic biomechanical properties (such as hyperelasticity, hysteresis and viscoelasticity) in-vivo had a serious adverse effect on our ability to optimise treatments or predict their outcome, and made it necessary to rely on average properties obtained ex-vivo.This project aims to make in-vivo measurement of corneal biomechanical properties a reality. It seeks to cover the research needs underpinning the development of this technology and address two fundamental questions that have prevented progress in this field. The two questions revolve around the extraction of the material's stress-strain behaviour from the overall cornea's response to mechanical actions. Once these obstacles are removed, the path to establish in-vivo measurement technology becomes straightforward.There are significant potential benefits that can be achieved if corneal biomechanical properties could be measured in-vivo. The examples include better design of implants to restore clear vision in keratoconus patients, better planning of refractive surgery procedures that currently result in unexpected aberrations in 1:7 of patients, and the ability to eliminate effect of corneal stiffness on intraocular pressure measurements, which are required for glaucoma management. These potential developments will mean significant benefits to patients, healthcare services and medical device manufacturers.The research starts with an experimental study to determine the regional variation of corneal and scleral hyperelasticity, hysteresis and viscoelasticity. The study will use 3D digital imaging of human eye globes subjected to cycles of both intraocular pressure and external applanation forces and aim to address the key gaps in knowledge in ocular biomechanics.With maps of biomechanical properties established, numerical analysis tools will be built to embody these maps, in addition to existing knowledge on the biomechanical, topographic and micro-structural characteristics of the human eye. The tools, which will be custom built, will be validated against ocular behaviour data obtained experimentally before using them to develop conceptual techniques to measure corneal biomechanics in-vivo.Two types of property measurement techniques, based on contact and non-contact methods, will be assessed. In both cases, corneal response to a mechanical action is correlated to corneal stress-strain behaviour. This exercise will focus on the key research questions, and aim to formalise an analysis procedure to extract the cornea's stress-strain behaviour from its mechanical response, and to exclude the effects of intraocular pressure and cornea's geometric parameters on the results.The results of the numerical study will be assessed using proof-of-concept prototypes both experimentally on human eye globes and on volunteers within a clinical setting. The tests are intended to validate the numerical findings, cast light onto the characteristics of ocular deformation under mechanical actions, and provide initial results which will be important for the conduct of future clinical studies on fully operational device prototypes.Overall, the project addresses a challenging problem that is affecting progress in several areas of patient care in ophthalmology. It seeks to overcome the main barriers to making the in-vivo measurement of corneal properties a reality. The project follows a systematic approach where necessary knowledge about ocular behaviour is generated and a predictive tool of ocular mechanical response built before assessing the property measurement methods. With the knowledge and understanding to be generated in this project, research and development can progress to embody the new technology into medical devices suitable for clinical use.