title: Replacement of Ahmed aqueous drainage devices in eyes with device-related complications.
abstract: OBJECTIVE
  To examine the results of removal and simultaneous replacement of Ahmed aqueous drainage devices (ADDs), which require removal due to complications.
  
  
  METHODS
  Noncomparative retrospective case series of 6 patients.
  
  
  RESULTS
  For the period from January 1999 to December 2007, 325 Ahmed ADD insertions were performed in 272 patients. From this, we identified 6 patients (1.8%) who underwent removal of an ADD for device-associated complications. All had replacement of the Ahmed ADD in a different quadrant at the same surgery. The mean time interval from the original valve insertion was 31.2 months (median, 32.5; range, 3 to 67 mo). The indication for tube removal was chronic uveitis in 3 patients, plate exposure in 2 patients, and tube exposure in 1 patient. We examined the results at 12 months postsimultaneous removal and replacement of the ADD and at final follow-up (median, 25 mo; range, 13 to 52 mo). The preoperative complications resolved in all cases, with the inflammation settling postoperatively in the patients with preoperative uveitis and no patients developing tube or plate exposure at last follow-up. The mean preoperative intraocular pressure (IOP) was 16.0 mm Hg (median, 15.0; range, 9 to 29 mm Hg). At 12 months and final review, the mean IOP was 10.8 mm Hg (median, 10.0; range, 1 to 24 mm Hg) and 11.0 mm Hg (median, 10.0; range, 3 to 24 mm Hg), respectively. The mean number of glaucoma medications preoperatively was 2.8 (median, 3.5; range, 0 to 5). This was reduced to 1.7 (median, 1.5; range, 0 to 4) at 12 months and 2.2 (median, 1.5; range, 0 to 5) at final follow-up. Of the 6 cases in this series, 4 (66.6%) were considered to have adequate IOP control postoperatively. One patient developed postoperative hypotony, with an IOP of 4 mm Hg and reduced vision due to hypotony maculopathy. This patient declined further surgical intervention. One patient had a preoperative IOP of 29 mm Hg on 4 drops and acetazolamide 250 mg b.i.d. At 14 months postsurgery, IOP was 24 mm Hg on 4 drops and the patient underwent insertion of a second ADD. At last follow-up 14 months later, IOP was 10 mm Hg on 4 drops. There were no other significant intraoperative or postoperative complications in this series.
  
  
  CONCLUSIONS
  In patients who require removal of Ahmed ADDs due to complications, removal of the offending ADD and replacement in another quadrant is effective in both resolving the complications and maintaining IOP control.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada. mic.smith@utoronto.ca
authors.forename: Michael
authors.initials: M
authors.lastname: Smith
authors.forename: Yvonne M
authors.initials: YM
authors.lastname: Buys
authors.forename: Graham E
authors.initials: GE
authors.lastname: Trope
mesh_terms: D000328:Adult; D000368:Aged; D020878:Device Removal; D005901:Glaucoma / Q000503:physiopathology / Q000601:surgery*; D020327:Glaucoma Drainage Implants / Q000009:adverse effects*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D008875:Middle Aged; D011183:Postoperative Complications; D019919:Prosthesis Implantation; D012086:Reoperation; D012189:Retrospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology