title: Preimplantation Flow Testing of Ahmed Glaucoma Valve and the Early Postoperative Clinical Outcome.
abstract: OBJECTIVE
  The Ahmed glaucoma valve (AGV) implant is designed to prevent early postoperative hypotony. There is evidence of variation in hypotony rates in clinical trials which may be due to surgical technique variation, entry site leakage or valve defects from 'over priming'. We describe a simple preimplantation gravity driven test to assess valve function after priming that may reduce hypotony rates.
  
  
  METHODS
  Retrospective case note review. An in vivo flow test of AGVs, based on the gravity driven test was introduced prior to implantation. The onset and offset of flow through the valve was measured by altering the height of a bottle of balanced saline solution. We rejected the AGV, if there was fluid still flowing at 10 cm (7 mm Hg) or if there was no flow at 17 cm of water (12 mm Hg). The AGV implantation surgery was without mitomycin C, with a 25G needle entry tract, a corneal or scleral patch graft tube cover and without intracameral viscoelastic.
  
  
  RESULTS
  Twenty Ahmed valves were implanted in 16 patients between July 2008 and October 2009. Test failure resulted in four AGV being rejected. The mean preoperative pressure was 29 mm Hg (range, 10-57 mm Hg) and the intraocular pressure (IOP) at 7 days postoperatively was 15 mm Hg (range, 3-52 mm Hg). Hypotony, defined as an IOP of less than 5 mm Hg on two consecutive assessments, was present in two eyes (10%).
  
  
  CONCLUSIONS
  In vivo flow testing is an important safety check for the AGV. There are also other mechanisms after implantation that can cause an unexpected high or low IOP. How to cite this article: Jones E, Alaghband P, Cheng J, Beltran-Agullo L, Lim KS. Preimplantation Flow Testing of Ahmed Glaucoma Valve and the Early Postoperative Clinical Outcome. J Current Glau Prac 2013;7(1):1-5.
authors.affiliation: Consultant, Department of Glaucoma, Accident and Emergency, Moorfields Hospital NHS Trust, London, United Kingdom.
authors.forename: Emma
authors.initials: E
authors.lastname: Jones
authors.affiliation: Glaucoma Research Fellow, Department of Ophthalmology, St Thomas' Hospital, London, United Kingdom.
authors.forename: Pouya
authors.initials: P
authors.lastname: Alaghband
authors.affiliation: Clinical Glaucoma Fellow, Department of Ophthalmology, St Thomas' Hospital, London, United Kingdom.
authors.forename: Jason
authors.initials: J
authors.lastname: Cheng
authors.affiliation: Clinical Glaucoma Fellow, Department of Ophthalmology, St Thomas' Hospital, London, United Kingdom.
authors.forename: Laura
authors.initials: L
authors.lastname: Beltran-Agullo
authors.affiliation: Consultant Ophthalmic Surgeon,Department of Ophthalmology Glaucoma Lead, St Thomas' Hospital, Westminster Bridge Road, London, SE1 7EH, United Kingdom.
authors.forename: Kin
authors.initials: K
authors.lastname: Sheng Lim
keywords: Adverse effects; Ahmed implant.; Aqueous shunt; Glaucoma; Methods