In vitro fluid dynamics of the Ahmed glaucoma valve modified with expanded polytetrafluoroethylene.

Journal Article (Journal Article)

PURPOSE: Long-term intraocular pressure reduction by glaucoma drainage devices (GDDs) is often limited by the fibrotic capsule that forms around them. Prior work demonstrates that modifying a GDD with a porous membrane promotes a vascularized and more permeable capsule. This work examines the in vitro fluid dynamics of the Ahmed valve after enclosing the outflow tract with a porous membrane of expanded polytetrafluoroethylene (ePTFE). MATERIALS AND METHODS: The control and modified Ahmed implants (termed porous retrofitted implant with modified enclosure or PRIME-Ahmed) were submerged in saline and gelatin and perfused in a system that monitored flow (Q) and pressure (P). Flow rates of 1-50 μl/min were applied and steady state pressure recorded. Resistance was calculated by dividing pressure by flow. RESULTS: Modifying the Ahmed valve implant outflow with expanded ePTFE increased pressure and resistance. Pressure at a flow of 2 μl/min was increased in the PRIME-Ahmed (11.6 ± 1.5 mm Hg) relative to the control implant (6.5 ± 1.2 mm Hg). Resistance at a flow of 2 μl/min was increased in the PRIME-Ahmed (5.8 ± 0.8 mm Hg/μl/min) when compared to the control implant (3.2 ± 0.6 mm Hg/μl/min). CONCLUSIONS: Modifying the outflow tract of the Ahmed valve with a porous membrane adds resistance that decreases with increasing flow. The Ahmed valve implant behaves as a variable resistor. It is partially open at low pressures and provides reduced resistance at physiologic flow rates.

Full Text

Duke Authors

Cited Authors

  • DeCroos, FC; Kondo, Y; Mordes, D; Lee, MR; Ahmad, S; Asrani, S; Allingham, RR; Olbrich, KC; Klitzman, B

Published Date

  • February 2011

Published In

Volume / Issue

  • 36 / 2

Start / End Page

  • 112 - 117

PubMed ID

  • 21281065

Pubmed Central ID

  • 21281065

Electronic International Standard Serial Number (EISSN)

  • 1460-2202

Digital Object Identifier (DOI)

  • 10.3109/02713683.2010.512115


  • eng

Conference Location

  • England