Numerical study of aqueous humor flow and iris deformation with pupillary block and the efficacy of laser peripheral iridotomy

Background: Disclosing the mechanism of primary angle closure glaucoma with pupillary block is important to the diagnosis as well as treatments, such as the laser peripheral iridotomy. Comparing with abundant clinical researches, there have been fewer quantitative studies of the aqueous humor flows with synechia iris configurations, and the efficacy of laser peripheral iridotomy in treating glaucoma.

Methods: Based on the mathematical models of aqueous humor flow and iris deformation, the flow fields were simulated by computational fluid dynamics with normal and synechia iris configurations (iris-lens gap of 30, 5 and 2 μm, respectively), and through one-way fluid-structure coupling technique the deformations of the iris under the flow field pressure were calculated by finite element analysis. The efficacy of glaucoma treatment with different orifice sizes was also investigated.

Findings: Results show that the pressure difference between anterior and posterior chambers and iris deformation increase dramatically with the iris-lens gap distance less than 5 μm, and when further decreasing this gap may lead the iris touch the cornea causing angle closure glaucoma with noticeable iris bombé. Laser peripheral iridotomy simulation results show that iridotomy size of 0.2 mm can effectively decrease the pressure difference across the iris and relieve iris bombé.

Interpretation: This is a biomechanical numerical study, and the results are reasonable compare to those of published works. It may shed additional light on the diagnosis and treatment of angle closure glaucoma with pupillary block.