Department of Aerospace and Mechanical Engineering, Viterbi School of Engineering, University of Southern California, Los Angeles, CA, USA.
USC Roski Eye Institute, Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles CA, USA.
Transl Vis Sci Technol. 2023 Jan 3;12(1):16. doi: 10.1167/tvst.12.1.16.
To study the relationship between the circumferential extent of angle closure and elevation in intraocular pressure (IOP) using a novel mechanistic model of aqueous humor (AH) flow.
AH flow through conventional and unconventional outflow pathways was modeled using the unified Stokes and Darcy equations, which were solved using the finite element method. The severity and circumferential extent of angle closure were modeled by lowering the permeability of the outflow pathways. The IOP predicted by the model was compared with biometric and IOP data from the Chinese American Eye Study, wherein the circumferential extent of angle closure was determined using anterior segment OCT measurements of angle opening distance.
The mechanistic model predicted an initial linear rise in IOP with increasing extent of angle closure which became nonlinear when the extent of closure exceeded around one-half of the circumference. The nonlinear rise in IOP was associated with a nonlinear increase in AH outflow velocity in the open regions of the angle. These predictions were consistent with the nonlinear relationship between angle closure and IOP observed in the clinical data.
IOP increases rapidly when the circumferential extent of angle closure exceeds 180°. Residual AH outflow may explain why not all angle closure eyes develop elevated IOP when angle closure is extensive.
This study provides insight into the extent of angle closure that is clinically relevant and confers increased risk of elevated IOP. The proposed model can be utilized to study other mechanisms of impaired aqueous outflow.
利用房水（AH）流动的新力学模型研究眼压（IOP）的闭角范围和升高之间的关系。
使用统一的 Stokes 和 Darcy 方程对传统和非常规流出途径的 AH 流动进行建模，并用有限元法求解。通过降低流出途径的通透性来模拟闭角的严重程度和闭角的周向范围。模型预测的 IOP 与中美眼研究的生物测量和 IOP 数据进行了比较，其中通过前节 OCT 测量的房角开口距离来确定闭角的周向范围。
力学模型预测，随着闭角范围的增加，IOP 会呈初始线性上升，当闭角范围超过圆周的一半左右时，IOP 会呈非线性上升。IOP 的非线性上升与角区开放区域 AH 流出速度的非线性增加有关。这些预测与临床数据中观察到的闭角与 IOP 之间的非线性关系一致。
当闭角范围超过 180°时，IOP 会迅速升高。残余的 AH 流出可能解释了为什么当闭角广泛存在时，并非所有闭角眼都会出现升高的 IOP。
本研究深入了解了临床上相关的闭角范围，并增加了 IOP 升高的风险。所提出的模型可用于研究其他房水流出受损的机制。
