title: Expanded polytetrafluoroethylene membrane alters tissue response to implanted Ahmed glaucoma valve.
abstract: OBJECTIVE
  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-microm 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 microm for PRIME-Ahmed versus 94.9 +/- 21.2 microm 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.
authors.affiliation: Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: Francis Char
authors.initials: FC
authors.lastname: DeCroos
authors.forename: Sameer
authors.initials: S
authors.lastname: Ahmad
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kondo
authors.forename: Jessica
authors.initials: J
authors.lastname: Chow
authors.forename: Daniel
authors.initials: D
authors.lastname: Mordes
authors.forename: Maria Regina
authors.initials: MR
authors.lastname: Lee
authors.forename: Sanjay
authors.initials: S
authors.lastname: Asrani
authors.forename: R Rand
authors.initials: RR
authors.lastname: Allingham
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Olbrich
authors.forename: Bruce
authors.initials: B
authors.lastname: Klitzman
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D003228:Conjunctiva / Q000098:blood supply / Q000473:pathology*; D005355:Fibrosis / Q000517:prevention & control; D005549:Foreign-Body Reaction / Q000517:prevention & control*; D020327:Glaucoma Drainage Implants; D007429:Intraocular Pressure / Q000502:physiology; D008422:Materials Testing; D011138:Polytetrafluoroethylene; D011183:Postoperative Complications; D011474:Prosthesis Design; D019919:Prosthesis Implantation; D011817:Rabbits; D014065:Tonometry, Ocular
chemical_list: D001672:Biocompatible Materials; D011138:Polytetrafluoroethylene