Risk Factors for Failure of Tube Shunt Surgery: A Pooled Data Analysis

Abstract

Purpose: To identify the risk factors associated with failure of tube shunt surgery.

Design: Pooled analysis of 3 prospective multicenter, randomized clinical trials.

Methods: A total of 621 patients with medically uncontrolled glaucoma were enrolled, including 276 from the Ahmed Baerveldt Comparison Study, 238 from the Ahmed Versus Baerveldt Study, and 107 from the tube group of the Tube Versus Trabeculectomy Study. Patients were randomized to treatment with an Ahmed glaucoma valve (model FP7) or Baerveldt glaucoma implant (model 101-350). The associations between baseline risk factors and tube shunt failure were assessed using a Cox proportional hazards regression model. The primary outcome measure was the rate of surgical failure defined as intraocular pressure (IOP) > 21 mmHg or reduced < 20% from baseline, IOP ≤ 5 mmHg, loss of light perception vision, reoperation for glaucoma, or removal of implant.

Results: The cumulative probability of failure after tube shunt surgery was 38.3% after 5 years. In multivariable analyses, baseline factors that predicted tube shunt failure included preoperative IOP (≤ 21 mmHg compared to IOP > 21 and ≤ 25 mmHg; HR, 2.34; 95% CI, 1.52-3.61; P < .001), neovascular glaucoma (HR, 1.79; 95% CI, 1.28-2.52; P = .001), randomized treatment (for Ahmed glaucoma valve; HR, 1.36; 95% CI, 1.04-1.78; P = .025), and age (for 10 year decrease in age; HR, 1.19; 95% CI, 1.09-1.31; P < .001).

Conclusions: Lower preoperative IOP, neovascular glaucoma, Ahmed implantation, and younger age were predictors of tube shunt failure. This Study provides the largest prospectively collected dataset on tube shunt surgery.

Figure 1.

Kaplan-Meier survival curve showing the cumulative probability of failure of tube shunt surgery.