We report on modeling and bench test results targeted at better understanding of valved glaucoma drainage devices (GDDs), a common current surgical treatment for glaucoma. A simple equivalent circuit is described to model fluid mechanical behavior of the aqueous humor in an eye with glaucoma, both before and after implantation of a valved GDD. Finite element method simulations (FEM), based on the lubrication-von Kármán model, are then performed to analyze the valve's mechanical and fluidic performance. Using nanoporous membranes to mimic the in vivo fibrous capsule, we have developed a microfluidic bench test to simulate the aqueous humor flow and the post-implantation fibrous tissue encapsulation around the GDD back plate. Our numerical and bench test results show that, contrary to the prevailing belief, the valve significantly contributes to the total pressure drop even after fibrous capsule formation. Furthermore, we show that bypassing the valve through a simple polyimide tube insertion will dramatically lower the intraocular pressure (IOP) after fibrous capsule formation. This may offer a new treatment option in some patients with advanced glaucoma.
Bibliographical noteFunding Information:
Manuscript received November 26, 2003; revised October 19, 2004. The work of B. Ziaie was supported by the National Science Foundation (NSF) under CAREER Award BES-0093604. Asterisk indicates corresponding author. *T. Pan is with the Department of Biomedical Engineering and the Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455 USA (e-mail: email@example.com).
- Ahmed Glaucoma Valve™
- Glaucoma drainage device