title: Intraoperative testing of opening and closing pressure predicts risk of low intraocular pressure after Ahmed glaucoma valve implantation.
abstract: OBJECTIVE
  The aim of this study was to assess whether intraoperative testing of silicone Ahmed glaucoma valves (AGVs) would identify valves with an increased risk of low postoperative intraocular pressure (IOP).
  
  
  METHODS
  In 30 consecutive cases of glaucoma surgery with AGV implantation, after priming the AGV, we intraoperatively measured the opening pressure A, closing pressure B, and re-opening pressure C using the active infusion pump of a phako-machine. IOP was checked postoperatively on the same day. Low IOP was defined as <5 mm Hg. Intraoperatively measured pressure characteristics of the valve function were analysed for their ability to predict postoperative IOP outcomes.
  
  
  RESULTS
  Opening A, closing B, and re-opening C pressures (mean, (SD)) were 18.4 (5.1), 8.3 (4.7), and 11.7 (4.8)mm Hg, respectively. Ten patients (33.3%) had low IOP. An opening pressure of ≤18 mm Hg predicted low postoperative IOP with a sensitivity (10/10) of 100% (95% CI, 69.2-100) and a specificity (13/20) of 65.0% (95% CI, 40.8-84.6).
  
  
  CONCLUSIONS
  AGVs have a high variability of opening, closing, and re-opening pressures. An opening pressure of ≤18 mm Hg, a closing pressure of ≤10 mm Hg, or a re-opening pressure of ≤11 mm Hg identified all patients with low postoperative IOP.
authors: Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne 16, Switzerland.
authors: F
authors: F
authors: Bochmann
authors: Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne 16, Switzerland.
authors: A
authors: A
authors: Kipfer
authors: Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne 16, Switzerland.
authors: J
authors: J
authors: Tarantino
authors: Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne 16, Switzerland.
authors: C
authors: C
authors: Kaufmann
authors: Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne 16, Switzerland.
authors: L
authors: L
authors: Bachmann
authors: Department of Ophthalmology, Cantonal Hospital of Lucerne, Lucerne 16, Switzerland.
authors: M
authors: M
authors: Thiel
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005901:Glaucoma / Q000601:surgery*; D020327:Glaucoma Drainage Implants; D006801:Humans; D007429:Intraocular Pressure; D007432:Intraoperative Period; D008422:Materials Testing; D008875:Middle Aged; D015814:Ocular Hypotension / Q000175:diagnosis* / Q000517:prevention & control; D011312:Pressure; D019919:Prosthesis Implantation; D012372:ROC Curve; D014065:Tonometry, Ocular