title: Flow Test to Predict Early Hypotony and Hypertensive Phase After Ahmed Glaucoma Valve (AGV) Surgical Implantation.
abstract: To assess the validity of a preimplantation flow test to predict early hypotony [intraocular pressure (IOP)≤5 mm Hg on 2 consecutive visits and hypertensive phase (HP) (IOP>21 mm Hg) after Ahmed Glaucoma Valve (AGV) implantation.
  
  
  
  Prospective interventional study on patients receiving an AGV. A preimplantation flow test using a gravity-driven reservoir and an open manometer was performed on all AGVs. Opening pressure (OP) and closing pressure (CP) were defined as the pressure at which fluid was seen to flow or stop flowing through the AGV, respectively. OP and CP were measured twice per AGV. Patients were followed for 12 weeks.
  
  
  
  In total, 20 eyes from 19 patients were enrolled. At 12 weeks the mean IOP decreased from 29.2±9.1 to 16.8±5.2 mm Hg (P<0.01). The mean AGV OP was 17.5±5.4 mm Hg and the mean CP was 6.7±2.3 mm Hg. Early (within 2 wk postoperative) HP occurred in 37% and hypotony in 16% of cases. An 18 mm Hg cutoff for the OP gave a sensitivity of 0.71, specificity of 0.83, positive predictive value of 0.71, and negative predictive value of 0.83 for predicting an early HP. A 7 mm Hg cutoff for the CP yielded a sensitivity of 1.0, specificity of 0.38, positive predictive value of 0.23, and negative predictive value of 1.0 for predicting hypotony.
  
  
  
  Preoperative OP and CP may predict early hypotony or HP and may be used as a guide as to which AGV valves to discard before implantation surgery.
authors.affiliation: *Khoo Tech Puat Hospital, Singapore, Singapore †Institut Català de la Retina, Barcelona, Spain ‡Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, University of Toronto, Toronto, ON, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Cheng
authors.forename: Laura
authors.initials: L
authors.lastname: Beltran-Agullo
authors.forename: Yvonne M
authors.initials: YM
authors.lastname: Buys
authors.forename: Edward B
authors.initials: EB
authors.lastname: Moss
authors.forename: Johanna
authors.initials: J
authors.lastname: Gonzalez
authors.forename: Graham E
authors.initials: GE
authors.lastname: Trope
mesh_terms: D000368:Aged; D001082:Aqueous Humor / Q000502:physiology*; D003941:Diagnostic Techniques, Ophthalmological; D005189:False Positive Reactions; D005260:Female; D005901:Glaucoma / Q000503:physiopathology / Q000601:surgery*; D020327:Glaucoma Drainage Implants; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis*; D015814:Ocular Hypotension / Q000175:diagnosis*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D019919:Prosthesis Implantation; D012680:Sensitivity and Specificity; D014065:Tonometry, Ocular; D016896:Treatment Outcome