Purpose: To study the impact of benzalkonium chloride (BAK) exposure from eye drops on subsequent time to trabeculectomy failure.
Patients and 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.