Elastohydrodynamics of the eyelid wiper
Elastohydrodynamics of the eyelid wiper
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DOI：
10.1007/s11538-007-9252-7
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发表时间：
2008-02-01
影响因子：
3.5
通讯作者：
Collins, M. J.
中科院分区：
文献类型：
--
作者：
Jones, M. B.;Fulford, G. R.;Collins, M. J.
建立了人体眼睑擦拭器的弹性流体动力学模型。将标准润滑理论应用于眼睑擦拭器和眼表面之间的流体层。润滑膜的作用是通过防止眼睑擦拭器和眼表面之间的固体与固体接触来降低剪切应力。为了使润滑膜有效，需要眼睑擦拭器的取向在眨眼的打开和关闭阶段之间改变。为了对此进行建模，将流体动力学模型与眼睑擦拭器和眼表面的软组织的弹性床垫模型耦合。这导致了一个一维的非线性偏微分方程控制的润滑膜中的流体压力。为了求解微分方程，必须指定载荷条件或约束方程。然后对所得系统进行数值求解。该模型允许预测的泪膜流量从上眼睑下，以及正常和剪切应力作用于眼表。这些因素与干眼症、角膜变形和接触透镜设计有关。发现眼睑下的压力和剪应力作用在约0.1 mm的长度上，这与临床观察一致。为了实现在眨眼期间从上眼睑下的眼泪的流动，该模型要求在眨眼的闭合阶段期间眼睑施加到眼表面的法向力显著高于在眨眼的打开阶段期间。
This paper presents an elastohydrodynamic model of the human eyelid wiper. Standard lubrication theory is applied to the fluid layer between the eyelid wiper and ocular surface. The role of the lubrication film is to reduce the shear stresses by preventing solid to solid contact between the eyelid wiper and ocular surface. For the lubrication film to be effective, it is required that the orientation of the eyelid wiper changes between the opening and closing phases of a blink. In order to model this, the hydrodynamic model is coupled with an elastic mattress model for the soft tissue of the eyelid wiper and ocular surface. This leads to a one-dimensional non-linear partial differential equation governing the fluid pressure in the lubrication film. In order to solve the differential equation, a loading condition or constraint equation must be specified. The resulting system is then solved numerically. The model allows predictions of the tear film flux from under the upper eyelid, as well as normal and shear stresses acting on the ocular surface. These factors are important in relation to dry eye syndrome, deformation of the cornea and contact lens design. It is found that the pressure and shear stress under the eyelid act across a length of approximately 0.1 mm which is consistent with clinical observations. It order to achieve a flow of tears from under the upper eyelid during a blink, the model requires that the normal force the eyelid applies to the ocular surface during the closing phase of the blink is significantly higher than during the opening phase of the blink.