Salimi S, Park S Simon, Freiheit T
Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
J Biomech Eng. 2011 Sep;133(9):091009. doi: 10.1115/1.4005166.
The vibration characteristics of shell structures such as eyes have been shown to vary with intraocular pressure (IOP). Therefore, vibration characteristics of the eye have the potential to provide improved correlation to IOP over traditional IOP measurements. As background to examine an improved IOP correlation, this paper develops a finite element model of an eye subject to vibration. The eye is modeled as a shell structure filled with inviscid pressurized fluid in which there is no mean flow. This model solves a problem of a fluid with coupled structural interactions of a generally spherically shaped shell system. The model is verified by comparing its vibrational characteristics with an experimental modal analysis of an elastic spherical shell filled with water. The structural dynamic effects due to change in pressure of the fluid are examined. It is shown that the frequency response of this fluid-solid coupled system has a clear increase in natural frequency as the fluid pressure rises. The fluid and structure interaction is important for accurate prediction of system dynamics. This model is then extended to improve its accuracy in modeling the eye by including the effect of the lens to study corneal vibration. The effect of biomechanical parameters such as the thicknesses of different parts of the eye and eye dimensions in altering measured natural frequencies is investigated and compared to the influence of biomechanical parameters in Goldmann applanation tonometry models. The dynamic response of the eye is found to be less sensitive to biomechanical parameters than the applanation tonometry model.
诸如眼睛等壳结构的振动特性已被证明会随眼内压（IOP）而变化。因此，与传统的眼压测量方法相比，眼睛的振动特性有可能与眼压具有更好的相关性。作为研究改进的眼压相关性的背景，本文建立了一个受振动影响的眼睛的有限元模型。眼睛被建模为一个充满无粘性加压流体且无平均流动的壳结构。该模型解决了一个具有一般球形壳系统的流体与结构耦合相互作用的问题。通过将其振动特性与一个充满水的弹性球壳的实验模态分析进行比较，对该模型进行了验证。研究了由于流体压力变化而产生的结构动力学效应。结果表明，随着流体压力升高，这种流固耦合系统的频率响应在固有频率上有明显增加。流体与结构的相互作用对于准确预测系统动力学很重要。然后扩展该模型，通过纳入晶状体的影响来研究角膜振动，以提高其对眼睛建模的准确性。研究并比较了诸如眼睛不同部位的厚度和眼睛尺寸等生物力学参数在改变测量的固有频率方面的作用，以及与戈德曼压平眼压计模型中生物力学参数的影响。结果发现，与压平眼压计模型相比，眼睛的动态响应对生物力学参数的敏感性较低。
