In vitro fluid dynamics of the Ahmed glaucoma valve modified with expanded polytetrafluoroethylene.
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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.
Glaucoma Drainage Implants
In Vitro Techniques
Published Version (Please cite this version)10.3109/02713683.2010.512115
Publication InfoAhmad, S; Allingham, Robert Rand; Asrani, S; DeCroos, FC; Klitzman, Bruce; Kondo, Y; ... Olbrich, KC (2011). In vitro fluid dynamics of the Ahmed glaucoma valve modified with expanded polytetrafluoroethylene. Curr Eye Res, 36(2). pp. 112-117. 10.3109/02713683.2010.512115. Retrieved from http://hdl.handle.net/10161/10348.
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Richard and Kit Barkhouser Professor of Ophthalmology, in the School of Medicine
Dr. Allingham has pursued both basic science and clinical research in the subspecialty of glaucoma. His major research interest is the study of genetic eye disorders, primarily the inherited glaucomas. The most common form of glaucoma (primary open-angle glaucoma or POAG) is believed to have a strong genetic component. He leads a large NIH funded study of which is directed at identifying the specific gene(s) responsible for glaucoma. Over 9,000 individuals have been enrolled in the Duk
This author no longer has a Scholars@Duke profile, so the information shown here reflects their Duke status at the time this item was deposited.
Professor of Ophthalmology
Sanjay Asrani, MD, specializes in glaucoma diagnosis and treatment, and cataract surgery. He is highly skilled in all forms of cataract and glaucoma surgery including tube implant, laser and filtering surgery. He is board certi­fied, fellowship trained, and has been honored among “America’s Top Ophthalmologists” and “Best Doctors in America”. Asrani is a dedicated researcher receiving support from Research to Prevent Blindness, private foundations, an
Associate Professor of Surgery
Our overriding interests are in the fields of tissue engineering, wound healing, biosensors, and long term improvement of medical device implantation. My basic research interests are in the area of physiological mechanisms of optimizing substrate transport to tissue. This broad topic covers studies on a whole animal, whole organ, hemorheological, microvascular, cellular, ultrastructural, and molecular level. The current projects include: 1) control of blood flow and flow distribu
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