Objective: The study was intended to determine methods that could evaluate in vitro the flow characteristics of glaucoma drainage devices.
Design: Two test methods were used: (1) a gravity-driven flow test and (2) a syringe-pump-driven flow test. Eighteen devices, both valved and nonvalved, from 4 manufacturers were evaluated for their hydrodynamic resistance and the pressure at which the flow becomes 0.
Outcome: Results show a wide variation in device performance, indicating a strong need for enhanced quality control procedures in the device manufacturing process.
Conclusion: A gravity-driven flow test provides a reasonably quick test of both resistance and closing pressure, which might be useful as a manufacturing line test. The syringe-driven flow test requires more time but provides additional insight into device performance, and, therefore, might be useful as a design validation test.