Functionality and Priming Stream Patterns of the Ahmed Glaucoma Valve in a Laboratory Setting.

Abstract

Purpose: To determine if there is a significant association between the steady state pressure of Ahmed Glaucoma Valves (AGVs) and the fluid pattern exhibited during the priming step of implantation.

Methods: In this experimental laboratory study, fifty AGVs were primed according to manufacturer guidelines by injecting balanced salt solution through a 27-gauge cannula. Group 1 consisted of 8 AGVs with a distinct stream priming pattern. Group 2 consisted of 7 AGVs without a distinct stream priming pattern (pooling). These valves were further tested using a perfusion system to measure steady-state pressure across the valve. A Student's t-test was used to assess the differences in mean steady-state pressures.

Results: 43/50 AGVs (86%) demonstrated a distinct stream of fluid during priming (group 1), while 7 (14%) showed a pooling of fluid only, without a focal stream (group 2). Steady-state pressure was achieved by 45 seconds for the 15 samples. The mean steady-state pressure (± standard deviation) at 60 seconds was 11.00 ± 1.90 mmHg for group 1 and 10.31 ± 2.53 mmHg for group 2 (p = 0.56), demonstrating no significant difference between groups.

Conclusion: The most common fluid pattern observed is a focal stream of fluid exiting the valve, with a minority exhibiting a slow pooling of fluid. The fluid pattern observed during AGV priming does not predict the valve's functionality, as both priming patterns resulted in similar steady-state pressures, which were consistently in line with manufacturer specifications.