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Comparative In Vitro Flow Study of 3 Different Ex-PRESS Miniature Glaucoma Device Models.
MedLine Citation:
PMID:  22274666     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
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) (µL/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 µm) showed a statistically significant higher flow rate and lower resistance compared with both the P-50 and R-50 models (internal diameter 50 µm) (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.
Authors:
Stephan Estermann; Kanokwan Yuttitham; Julie A Chen; On-Tat Lee; Robert L Stamper
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-1-20
Journal Detail:
Title:  Journal of glaucoma     Volume:  -     ISSN:  1536-481X     ISO Abbreviation:  -     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-1-25     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9300903     Medline TA:  J Glaucoma     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
*Department of Ophthalmology, University of California San Francisco (UCSF), San Francisco, CA †Augenklinik Stadtspital Triemli, Zurich, Switzerland.
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