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.