Khoobyar Anahid, Penkova Anita N, Humayun Mark S, Sadhal Satwindar Singh
Department of Aerospace and Mechanical Engineering, University of Southern California, USC Viterbi School of Engineering, Los Angeles, CA 90089-1453.
Department of Aerospace and Mechanical Engineering, USC Viterbi School of Engineering, Los Angeles, CA 90089-1453; Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027.
J Heat Transfer. 2022 Mar 1;144(3):031208. doi: 10.1115/1.4053197. Epub 2022 Feb 7.
The purpose of this study is to investigate the effect of partial liquefaction (due to ageing) of the vitreous humor on the transport of ocular drugs. In our model, the gel part of the vitreous is treated as a Darcy-type porous medium. A spherical region within the porous part of vitreous is in a liquid state which, for computational purposes, is also treated as a porous medium but with a much higher permeability. Using the finite element method, a time-dependent, three-dimensional model has been developed to computationally simulate (using the Petrov-Galerkin method) the transport of intravitreally injected macromolecules where both convection and diffusion are present. From a fluid physics and transport phenomena perspective, the results show many interesting features. For pressure-driven flow across the vitreous, the flow streamlines converge into the liquefied region as the flow seeks the fastest path of travel. Furthermore, as expected, with increased level of liquefaction, the overall flow rate increases for a given pressure drop. We have quantified this effect for various geometrical considerations. The flow convergence into the liquefied region has important implication for convective transport. One effect is the clear diversion of the drug as it reaches the liquefied region. In some instances, the entry point of the drug in the retinal region gets slightly shifted due to liquefaction. While the model has many approximations and assumptions, the focus is illustrating the effect of liquefaction as one of the building blocks toward a fully comprehensive model.
本研究的目的是调查玻璃体液（由于老化）的部分液化对眼部药物运输的影响。在我们的模型中，玻璃体的凝胶部分被视为达西型多孔介质。玻璃体多孔部分内的一个球形区域处于液态，为了计算目的，该区域也被视为多孔介质，但渗透率要高得多。使用有限元方法，开发了一个随时间变化的三维模型，以通过计算模拟（使用彼得罗夫-伽辽金方法）玻璃体内注射的大分子的运输，其中同时存在对流和扩散。从流体物理学和传输现象的角度来看，结果显示出许多有趣的特征。对于穿过玻璃体的压力驱动流，当流体寻求最快的行进路径时，流线会汇聚到液化区域。此外，正如预期的那样，随着液化程度的增加，在给定的压力降下，总体流速会增加。我们已经针对各种几何因素对这种影响进行了量化。流体汇聚到液化区域对对流传输具有重要意义。一个影响是药物到达液化区域时明显的转向。在某些情况下，由于液化，药物在视网膜区域的进入点会略有偏移。虽然该模型有许多近似和假设，但重点是说明液化作为构建一个完全综合模型的基石之一的影响。
