Trabeculectomy with Mitomycin C: Outcomes and Risk Factors for Failure in Phakic Open-Angle Glaucoma

Abstract

To evaluate long-term tonometric outcomes of trabeculectomy with adjunctive mitomycin C (MMC) and its efficacy in achieving a range of intraocular pressures (IOP) in phakic patients with open-angle glaucoma. Retrospective cohort study. Three levels of success were defined by these criteria: (A) IOP < or =18 mmHg and IOP reduction of 20%; (B) IOP < or =15 mmHg and IOP reduction of 25%; and (C) IOP < or =12 and IOP reduction of 30%. Kaplan-Meier survival analyses were used to assess outcomes. Cox's proportional hazard regression analysis was used to identify risk factors for failure. Two hundred twenty-five phakic patients (292 eyes) with open-angle glaucoma, > or =40 years of age at time of trabeculectomy. The primary outcome was qualified success rate (with or without medications) according to the defined criteria. Secondary outcomes include IOP level and number of medications at 1 and 3 years after surgery, postoperative complications, and need for further glaucoma surgery. Mean IOP (+/-standard deviation) decreased from 18.8 mmHg (+/-6.1 mmHg) before surgery to 11.3 mmHg (+/-4.5 mmHg) at 1 year and 11.1 mmHg (+/-4.2 mmHg) at 3 years (P<0.001 for both). The mean number of medications decreased from 2.8 (+/-1.0) to 0.4 (+/-0.7) at 1 year and 0.7 (+/-1.0) at 3 years (P<0.001 for both). The success rates were 85%, 84%, and 79% at 1 year for criteria A, B, and C, respectively; and 62%, 56%, and 46% for these criteria, respectively, at 3 years. Postoperative laser suture lysis was associated with a higher rate of failure for criteria B and C (P<0.001 for both), the hazard ratio (HR) was 1.7 for criteria B and 2.0 for criteria C. Prior argon laser trabeculoplasty was associated with higher risk of failure for criteria C (HR = 1.6; P = 0.05). Trabeculectomy with MMC effectively reduces IOP in phakic open-angle glaucoma, but long-term low IOPs are achieved in only half of the cases. Laser suture lysis after trabeculectomy and prior argon laser trabeculoplasty are associated with a higher risk of failure when low IOPs are required.