"金标准"眼压计的力学缺陷和固液膜解耦原理与实现

Intraocular pressure (IOP) is an important indicator for diagnosing glaucoma, and it is an essential parameter to show the intraocular status. It is not directly measureable due to its inner attribute; hence, the tonometers exist now all utilize the outer response of the cornea to obtain IOP. The measurement of IOP is done in vivo, and its magnitude of 10 mmHg, which require the tonometer to have a resolution of 1‰ atm. Goldmann applanation tonometer (GAT) is considered as a “gold standard” in IOP measurement, however, it bases on the assumption of the cancelation of reaction force of cornea and surface tension force of tears. The assumption highly depends on the properties of cornea (elastic modulus) and tears, which are difficult to be determined. This assumption would cause the IOP measured to be lower than the actual situation, with a magnitude that could reach the critical pressure to cause the damage of optic nerve, which will greatly jeopardize the diagnose and treatment of glaucoma. This proposal aims to fix the defects of GAT in mechanics, by utilizing the depth-sensing technology, to investigate the mechanical response of solid (cornea) and liquid (tears) membrane. A new method that relies on multiple depth measurements will be proposed to decouple the effect of cornea and tears from IOP, which will be fulfilled by modifications to the indenter. A prototype of the proposed tonometer will be manufactured based on the new design, which will give reliable measures of the actual IOP, and can reduce the error in diagnoses and treatments in ophthalmology, which makes this proposal important in both scientific significance and practical applications.

眼压是青光眼诊断的重要指标，是反映眼内状态的基本参量。由于它无法直接测得，现有眼压计都通过外部响应进行反演。眼压测量要求在体原位；其值在10mmHg量级，要求仪器有较高测量精度 (约1‰大气压)。现有眼压计以Goldmann眼压计为“金标准”，然而它的测量原理，采取了笼统地将角膜反力和泪膜张力(方向相反)完全抵消的处理方案。两力抵消与否，实际上与难以确定的角膜(弹性模量)和泪膜的性质密切相关。这种处理方案可导致眼压测量值低估，达到造成视神经损伤的量级，严重影响青光眼的诊断和治疗。本申请针对“金标准”眼压计上述力学缺陷，基于深度敏感技术，深入分析固膜(角膜)和液膜(泪膜)的力学响应；提出借助压入深度，解耦固、液膜对眼压作用的原理；利用测压头标定面积，实现多深度测量方案；设计和研制新型眼压计原型，以获得真实可靠的眼压，防止因眼压测量误差造成眼科诊疗错误，具有重要的科学意义和应用价值。

本项目从现有眼科“金标准”的Goldmann眼压计测量原理基础存在的问题出发，通过实验、模拟的结合，证实了现有压平眼压计测量原理中角膜反力和泪膜张力完全抵消的假设不成立，确定了泪膜张力一般比角膜反力小一个量级，提出了考虑角膜几何和材料的眼内压测量方法。实验上制备了不同性质含水高分子材料及人工角膜结构，测定不同内压下的压平载荷与压缩位移、接触半径的关系，结合角膜地形仪等测定人工角膜几何形貌，并在猪眼球上验证了研究提出的测量原理的可靠性；模拟上采用有限元分析了角膜反力与几何、材料和内压的定量关系，并采用多物理模拟，分析了压平过程中泪膜铺展形状和压力分布。此研究结果将为获得真实可靠的眼压和基于新原理的眼压计的研制提供基础，防止因眼压测量误差贻误眼压诊断和青光眼治疗，因此具有重要的科学意义和应用价值。