Expanded Polytetrafluoroethylene Membrane Alters Tissue Response to Implanted Ahmed Glaucoma Valve

• Published in: Current eye research Vol. 34; no. 7; pp. 562 - 567
• Main Authors: DeCroos, Francis Char, Ahmad, Sameer, Kondo, Yuji, Chow, Jessica, Mordes, Daniel, Lee, Maria Regina, Asrani, Sanjay, Allingham, R. Rand, Olbrich, Kevin C., Klitzman, Bruce
• Format: Journal Article
• Language: English
• Published: England Informa UK Ltd 01.01.2009; Taylor & Francis
• Subjects: Animals; Biocompatible Materials; Conjunctiva - blood supply; Conjunctiva - pathology; Fibrosis - prevention & control; foreign-body reaction; Foreign-Body Reaction - prevention & control; glaucoma; glaucoma drainage implant; Glaucoma Drainage Implants; Intraocular Pressure - physiology; Materials Testing; Polytetrafluoroethylene; Postoperative Complications; Prosthesis Design; Prosthesis Implantation; Rabbits; Tonometry, Ocular
• ISSN: 0271-3683; 1460-2202
• DOI: 10.1080/02713680902963167

Purpose: Long-term intraocular pressure control by glaucoma drainage implants is compromised by the formation of an avascular fibrous capsule that surrounds the glaucoma implant and increases aqueous outflow resistance. It is possible to alter this fibrotic tissue reaction and produce a more vascularized and potentially more permeable capsule around implanted devices by enclosing them in a porous membrane. Methods: Ahmed glaucoma implants modified with an outer 5-μ m pore size membrane (termed porous retrofitted implant with modified enclosure or PRIME-Ahmed) and unmodified glaucoma implants were implanted into paired rabbit eyes. After 6 weeks, the devices were explanted and subject to histological analysis. Results: A tissue response containing minimal vascularization, negligible immune response, and a thick fibrous capsule surrounded the unmodified Ahmed glaucoma implant. In comparison, the tissue response around the PRIME-Ahmed demonstrated a thinner fibrous capsule (46.4 ± 10.8 μ m for PRIME-Ahmed versus 94.9 ± 21.2 μ m for control, p < 0.001) and was highly vascularized near the tissue-material interface. A prominent chronic inflammatory response was noted as well. Conclusions: Encapsulating the aqueous outflow pathway with a porous membrane produces a more vascular tissue response and thinner fibrous capsule compared with a standard glaucoma implant plate. Enhanced vascularity and a thinner fibrous capsule may reduce aqueous outflow resistance and improve long-term glaucoma implant performance.