Purchase this article with an account.
S. Estermann, K. Yuttitham, R. L. Stamper; Comparative Flow Study of 3 Different Models of Ex-PRESS Drainage Devices. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4895.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine flow characteristics of 3 models of Ex-PRESS drainage devices at different levels of pressure under in vitro conditions.
Three different models of Ex-PRESS drainage devices, P-50, R-50 and P-200 (Optonol Ltd.) were tested at 5 different levels of pressure (5, 10, 15, 20, 25mmHg) in a gravity driven flow test. Four measurements per sample over a 15 minutes period were performed. The experimental set-up was based on a gravity driven flow test where the Ex-PRESS device was subjected to a constant gravitational force of fluid. The apparatus consisted of a water column that was occluded with Parafilm "M", a water reservoir, and a scale. The Ex-PRESS device itself was implanted into the Parafilm "M" under a microscope. The drainage was collected in a beaker which was continuously weighed with a precision scale. Flow (Q) was calculated as grams of balanced salt solution (BSS) per minute at each pressure level and then converted to ml/min. All tests were done with balanced salt solution at a temperature of 22° C.
Based on these measurements the flow rate for the P-50 model was 0.18 ± 0.001 ml/min (mean ± SD) at 5mmHg, 0.35 ± 0.002 at 10mmHg, 0.47 ± 0.001 at 15mmHg, 0.58 ± 0.004 at 20mmHg, and 0.69 ± 0.004 at 25mmHg. For the R-50 model Q was 0.14 ± 0.004 at 5mmHg, 0.26 ± 0.01 at 10mmHg, 0.40 ± 0.002 at 15mmHg, 0.51 ± 0.003 at 20mmHg, and 0.62 ± 0.007 ml/min at 25mmHg. For the P-200 model Q was 0.63 ± 0.002 at 5mmHg, 1.15 ± 0.01 at 10mmHg, 1.54 ± 0.002 at 15mmHg, 1.89 ± 0.005 at 20mmHg, and 2.2 ± 0.01 ml/min at 25mmHg. A comparison of the flow rates among the 3 models showed significant differences (p < 0.05) at all pressure levels.
The currently available models of Ex-PRESS drainage devices differed significantly in their flow characteristics with the P-200 showing the highest flow rate followed by the P-50 and the R-50.
This PDF is available to Subscribers Only