Effect of Anterior Chamber Depth on Shear Stress Exerted on Corneal Endothelial Cells by Altered Aqueous Flow after Laser Iridotomy

Abstract

Purpose. The study hypothesis was that shear stress caused by abnormal aqueous flow is one of the causes of corneal endothelial cell loss after laser iridotomy (LI). The shear stress exerted on the corneal endothelial cells (CECs) in anterior chambers (ACs) of different depths was calculated by a computational fluid dynamics program. The effect of shear stress was also examined on human corneal endothelial cells (HCECs) grown on microscope slides. Methods. Three-dimensional models of the AC were constructed, with and without an LI window, and AC depths of 2.8, 1.8, 1.5, and 1.0 mm. The speed of aqueous streaming through the LI window was obtained from animal studies and used to calculate the shear stress exerted on the CECs. Cultured HCECs attached to glass slides were subjected to different magnitudes of shear stress by exposing the cells to different flow rates of the culture solution. The number of cells remaining attached to the slide under each condition was determined. Results. The shear stresses were 0.14, 0.31, 0.48, and 0.70 dyn/cm(2) for models with AC depths of 2.8, 1.8, 1.5, and 1.0 mm, respectively. When cultured HCECs were subjected to shear stress within the range calculated by the three-dimensional models, the number of cells remaining attached to the glass slide decreased as the magnitude and duration of the shear stress increased. Conclusions. Shear stress exerted on CECs after LI may reach a magnitude high enough to cause cell damage and loss in eyes, especially in those with shallow anterior chambers.

Phakic Iris-Fixated Intraocular Lens Placement in the Anterior Chamber: Effects on Aqueous Flow

“…Yamamoto et al 15 used PIV (particle image velocimetry) to measure the flow of aqueous humor through a laser iridotomy hole during miosis in rabbits. These results were used by Yamamoto et al 16 to prescribe the inlet velocity of an iridotomy jet in their numerical model of flow in the anterior chamber, which they assumed to be the first quarter-period of a cosine curve. They used a hole of diameter d LI ¼ 0.56 mm for which the measured maximum velocity was u max ¼ 9.39 mm/s, and took the duration to be the average duration of miosis in humans after light stimulation, 17 giving T jet ¼ 0.66 seconds.…”

“…If we assume that, during miosis in an eye with an iridotomy, the volumetric flux through the iris-lens channel is negligible compared to that through the iridotomy hole, it would suggest that the estimates of volumetric flux through the iridotomy in the experiments of Yamamoto et al 15 could be similar to the volumetric flux through the iris-lens channel in the natural eye. We therefore adopt the formula used by Yamamoto et al 16 and impose the following time-dependent total volumetric flux through the iris-lens channel in our simulations of miosis in the natural eye:…”

“…(a) Flux from the posterior to the anterior chamber of the eye generated during miosis. The intensity of the flux is based on the measurements by Yamamoto et al16 on rabbit eyes. (b) Angular velocity of the eye globe versus time during saccadic rotations for two different saccadic rotations with amplitudes 108 and 208.…”

Changes in Extracellular Matrix Gene and Protein Expressions in Human Trabecular Meshwork Cells in Response to Mechanical Fluid Flow Stimulation

“…Previously, fluid flow stress was reported to affect the pathological condition or homeostasis in some ocular tissues, e.g., flow stress on cultured human corneal epithelial cells affected TGF-β signaling, which may be associated with a delayed wound-healing mechanism during blinking [20]. Flow stress also can cause corneal endothelial cell damage or loss after laser iridotomy [23] or gene expression of endovascular cells, which may contribute to the vasoregulatory and antithrombotic properties of the retinal vessels [18]. Although the current study focused on mechanical stimulation of the fluid flow on the HTM cells, a previous report also investigated the responses of HTM cells exposed to shear stress.…”

Análisis, por Simulación, de los Esfuerzos Cortantes en la Superficie del Iris, en Presencia de Lentes Fáquicos Intraoculares

“…En los últimos años se han realizado estudios analíti-cos y numéricos del flujo del humor acuoso dentro del ojo [9,10,11] . Siggers y Ethier [12] presentan una amplia revisión de los mecanismos asociados a la dinámica de fluidos dentro del ojo.…”