title: Preservative exposure and surgical outcomes in glaucoma patients: The PESO study.
abstract: OBJECTIVE
  To study the impact of benzalkonium chloride (BAK) exposure from eye drops on subsequent time to trabeculectomy failure.
  
  
  METHODS
  Retrospective chart review of 128 glaucoma patients who had undergone a trabeculectomy between 2004 and 2006. The number and type of ophthalmic drops used preoperatively and relevant demographics were recorded. Surgical failure criteria included inadequate pressure lowering or need for postoperative ocular antihypertensives, laser trabeculoplasty, 5-fluorouracil needling, or repeated surgery. Patients were examined for these criteria over a minimum postoperative period of 2 years. Data were assessed using Kaplan-Meier and Cox regression models.
  
  
  RESULTS
  Complete surgical success was achieved in 47.7% of patients. Patients received between 1 and 8 BAK-containing drops daily, with a median of 3. Time to surgical failure in patients receiving higher preoperative daily doses of BAK was shorter than in patients who had less BAK exposure (P=0.008). Proportional hazard modeling identified uveitic and neovascular glaucoma as significant confounders of the univariate model (P=0.024), although the main effect of BAK exposure was maintained with a hazard ratio of 1.21 (P=0.032). The number of different medications used to control intraocular pressure did not significantly affect survival time in a secondary Cox model (P=0.948).
  
  
  CONCLUSIONS
  Increased preoperative exposure to ophthalmic solutions preserved with BAK is a risk factor for earlier surgical failure, independent of the number of medications used. This study extends earlier findings of potential adverse effects of ophthalmic preservatives on surgical outcomes to the modern pharmacopeia used in the medical management of glaucoma.
authors.affiliation: *Faculty of Medicine, University of Toronto †Department of Ophthalmology and Vision Sciences, University of Toronto and Sunnybrook Health Sciences Centre, Toronto, ON, Canada.
authors.forename: Corey
authors.initials: C
authors.lastname: Boimer
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Birt
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001548:Benzalkonium Compounds / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005901:Glaucoma / Q000188:drug therapy / Q000601:surgery*; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009883:Ophthalmic Solutions; D011183:Postoperative Complications; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects*; D012189:Retrospective Studies; D012307:Risk Factors; D014130:Trabeculectomy; D017211:Treatment Failure; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000959:Antihypertensive Agents; D001548:Benzalkonium Compounds; D009883:Ophthalmic Solutions; D011310:Preservatives, Pharmaceutical