Elsheikh Ahmed, Wang Defu, Kotecha Aachal, Brown Michael, Garway-Heath David
Division of Civil Engineering, Faculty of Engineering, University of Dundee, Dundee, DD1 4HN, UK.
Ann Biomed Eng. 2006 Oct;34(10):1628-40. doi: 10.1007/s10439-006-9191-8. Epub 2006 Sep 28.
Goldmann applanation tonometry (GAT) is the internationally accepted standard for intra-ocular pressure (IOP) measurement, which is important for the diagnosis of glaucoma. The technique does not consider the effect of the natural variation in the corneal thickness, curvature and material properties. As these parameters affect the structural resistance of the cornea, their variation is expected to lead to inaccuracies in IOP determination. Numerical Analysis based on the finite element method has been used to simulate the loading conditions experienced in GAT and hence assess the effect of variation in corneal parameters on GAT IOP measurements. The analysis is highly nonlinear and considers the hyper-elastic J-shaped stress-strain properties of corneal tissue observed in laboratory tests. The results reveal a clear association between both the corneal thickness and material properties, and the measured IOP. Corneal curvature has a considerably lower effect. Similar trends have been found from analysis of clinical data involving 532 patients referred to the Glaucoma Unit at Moorfields Hospital, and from earlier mathematical analyses. Nonlinear modelling is shown to trace the behaviour of the cornea under both IOP and tonometric pressure, and to be able to provide additional, and potentially useful, information on the distribution of stress, strain, contact pressure and gap closure.
Goldmann压平眼压计（GAT）是国际公认的眼内压（IOP）测量标准，这对青光眼的诊断很重要。该技术未考虑角膜厚度、曲率和材料特性自然变化的影响。由于这些参数会影响角膜的结构阻力，预计它们的变化会导致眼压测定不准确。基于有限元法的数值分析已被用于模拟GAT中所经历的加载条件，从而评估角膜参数变化对GAT眼压测量的影响。该分析具有高度非线性，并考虑了实验室测试中观察到的角膜组织的超弹性J形应力-应变特性。结果显示角膜厚度和材料特性与测量的眼压之间存在明显关联。角膜曲率的影响要小得多。从对 Moorfields 医院青光眼科转诊的 532 名患者的临床数据分析以及早期的数学分析中也发现了类似趋势。非线性建模显示能够追踪角膜在眼压和眼压计压力作用下的行为，并能够提供有关应力、应变、接触压力和间隙闭合分布的额外且可能有用的信息。
