Comparative In Vitro Flow Study of 3 Different Ex-PRESS Miniature Glaucoma Device Models

作者：Estermann Stephan; Yuttitham Kanokwan; Chen Julie A; Lee On Tat; Stamper Robert L^*

来源：Journal of Glaucoma, 2013, 22(3): 209-214.

DOI：10.1097/IJG.0b013e31824479ce

• Ex-PRESS miniature glaucoma device models
• comparative in vitro flow test
• flow properties
• calculation of resistance
• gravity-driven flow test

Purpose: To determine the flow characteristics of the 3 different models of the Ex-PRESS miniature glaucoma device in a controlled laboratory study.
Materials and Methods: The 3 different Ex-PRESS models (P-50, R-50, and P-200; Optonol Ltd; now Alcon Lab) were tested using a gravity-driven flow test. Three samples of each of the 3 Ex-PRESS models were subjected to a constant gravitational force of fluid at 5 different pressure levels (5 to 25 mm Hg). Four measurements per sample were taken at each pressure level. The main outcome measure was flow rate (Q) (mu L/min). Resistance (R) was calculated by dividing pressure (P) by the measured flow (Q).
Results: The flow rate was primarily pressure dependent. The P-200 model (internal diameter 200 mm) showed a statistically significant higher flow rate and lower resistance compared with both the P-50 and R-50 models (internal diameter 50 mm) (P < 0.0001). The P-50 and R-50 models demonstrated similar flow rates (P = 0.08) despite their difference in tube length (2.64 vs. 2.94 mm).
Conclusions: The 3 models of the Ex-PRESS mini shunt behaved in vitro as simple flow resistors by creating a relatively constant resistance to flow. Tube diameter was the only parameter with significant impact on flow and resistance. All models demonstrated flow rates per unit of pressure much higher than the outflow facility of a healthy human eye. Key Words: Ex-PRESS miniature glaucoma device models, comparative in vitro flow test, flow properties, calculation of resistance, gravity-driven flow test

• 出版日期2013-3