Trabeculectomy with mitomycin C: outcomes and risk factors for failure in phakic open-angle glaucoma

Abstract

Purpose: 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.

Design: Retrospective cohort study.

Methods: 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.

Participants: Two hundred twenty-five phakic patients (292 eyes) with open-angle glaucoma, > or =40 years of age at time of trabeculectomy.

Main outcome measures: 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.

Results: 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).

Conclusions: 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.