Postoperative flat anterior chamber: Incidence, risk factors, and effect on the long-term success of trabeculectomy

Purpose: To investigate the long-term effects of postoperative flat anterior chamber (FAC) development on outcomes following trabeculectomy with mitomycin C. Methods: This was a retrospective cohort study. Data on 383 consecutive patients (383 eyes) who underwent trabeculectomy at our institution between 1999 and 2009 were followed up. Patients who developed FAC after trabeculectomy and patients with maintained anterior chamber were evaluated. The primary outcome variable was the success of the initial trabeculectomy, which was defined at 3 different levels by the achievement of the following intraocular pressure (IOP)-related criteria without secondary IOP-lowering surgery: (a) IOP ≤ 12 mmHg and ≤30 % reduction in IOP from the preoperative level; (b) IOP ≤ 16 mmHg and ≤20 % reduction in IOP; and (c) IOP ≤ 21 mmHg. The hazard ratios (HRs) for the failure of trabeculectomy caused by FAC within 5 years of surgery were examined in conjunction with the Cox proportional hazards regression model. Results: FAC was observed in 90 of the 383 eyes examined (23.4 %). Postoperative mild FAC was associated with the long-term success of trabeculectomy when evaluated according to our strictest success criterion, Criterion-A [HR = 0.72 (95 % CI 0.53-0.98); P = 0.04]. In contrast, severe FAC was inversely associated with the long-term success of the surgery when evaluated according to our most lenient criterion, Criterion-C [HR = 1.93 (95 % CI 1.16-3.22); P = 0.01]. Conclusion: Mild postoperative FAC after trabeculectomy is associated with a favorable long-term outcome, whereas severe postoperative FAC leads to an unfavorable prognosis.