喷气试验中角膜生物力学效应影响因素的有限元分析

目的:研究喷气试验中眼内压、喷气压力以及巩膜材料对角膜生物力学效应的影响。方法:基于全眼三维模型及轴对称的喷气模型进行有限元分析，根据角膜前表面位移云图结果，结合曲面拟合等方法，分析角膜形态学参数变化，定量分析眼内压、喷气压力以及巩膜材料对角膜生物力学效应的影响。结果:当喷气压力峰值以及巩膜刚度一定，改变眼内压时，眼内压为24 mmHg相对于12 mmHg时的最大凹陷角膜顶端位移减少13%，角膜前表面反向曲率半径增加7.3%；眼内压以及巩膜刚度一定，改变喷气压力时，喷气压力峰值为60 kPa相对于20 kPa时的最大凹陷角膜顶端位移增加2.1倍，角膜前表面反向曲率半径减小0.68倍；眼内压以及喷气压力峰值一定，巩膜刚度为基准3倍相对于1/3倍时的最大凹陷角膜顶端位移减少26.8%。结论:角膜形变是角膜生物力学特性的反映，是由眼内压、角膜与巩膜材料以及外力作用共同决定，当其中任一参数发生变化，则影响角膜的生物力学效应。

Influencing factors of corneal biomechanical effect in air-puff test: a finite-element study

Abstract: Objective To study the effects of intraocular pressure, air-jet pressure and scleral material on corneal biomechanical effect in Air-puff Test. Method Based on the whole-eye three-dimensional model and the axisymmetric jet model, the finite element analysis was performed. According to the displacement nephogram on anterior corneal surface and combined with surface fitting and other methods, the changes of corneal morphological parameters were analyzed. In addition, the effects of intraocular pressure, air jet pressure and scleral material on corneal biomechanical effect were quantitatively analyzed. Results When the peak pressure of ejection and scleral stiffness kept constant, intraocular pressures increase from 12 mmHg to 24 mmHg made the maximum apical displacement of the cornea reduced by 13%, and the value of the curvature radius of the anterior corneal surface increased by 7.3%. When the intraocular pressure and the scleral stiffness remained constant, the peak pressure of ejections increase from 20 kPa to 60 kPa made the maximum apical displacement of the cornea increased by 2.1 times, and the curvature radius of the anterior surface reduced by 0.68 times. When the intraocular pressure and gas ejection pressure peak remained constant, the scleral stiffnesss increase from 1/3 times to 3 times of the baseline made the maximum apical displacement of the cornea reduced by 26.8%. Conclusion Corneal deformation was a reflection of the biomechanical properties of the cornea. It was determined by the combination of IOP, corneal and scleral materials, and external forces. When any of these parameters changed, the biomechanics effect of the cornea was altered. Keywords: air-puff test cornea biomechanics effect finite element analysis