Glaucoma drainage device more reliable than trabeculectomy for IOP control at 1 year

Aqueous tube shunts are significantly more likely to maintain IOP control without persistent hypotony than trabeculectomy with mitomycin-C at 1 year postop, according to results from the Tube Versus Trabeculectomy Study. However, both procedures produce similar IOP reductions, the study authors said.

"The results of the TVT (Tube Versus Trabeculectomy) Study suggest that consideration should be given to expanding the role of tube shunts in the surgical management of glaucoma," they noted.

Steven J. Gedde, MD, of Bascom Palmer Eye Institute in Miami, and investigators at 17 centers in the United States and United Kingdom reviewed outcomes of 212 glaucomatous eyes of 212 patients randomly assigned to undergo trabeculectomy or implantation with a 350 mm² Baerveldt glaucoma implant.

Their results are published in the January issue of American Journal of Ophthalmology.

The study included patients age 18 to 85 years who had glaucoma with uncontrolled IOP between 18 mm Hg and 44 mm Hg. All patients were being treated with the maximally tolerated number of glaucoma medications and had previously undergone a failed trabeculectomy or cataract surgery, according to the study.

The researchers calculated a 13.5% cumulative 1-year failure rate in the trabeculectomy group, significantly higher than the 3.9% failure rate in the tube group (P = .017).

"Nonvalved tube shunt surgery was more likely to maintain IOP control and avoid persistent hypotony or reoperation for glaucoma than trabeculectomy with MMC," the authors said. "The low failure rate in the tube shunt group compared with previous studies of tube shunts may relate to refinements in surgical technique, as well as differences in the length of follow-up and study populations."

At 1 year follow-up, both groups had similar IOPs, averaging 12.4 mm Hg in the tube group and 12.7 mm Hg in the trabeculectomy group (P = .73).

"Both surgical procedures produced similar IOP reductions at 1 year, but there was less need for supplemental medical therapy following trabeculectomy," the authors said.

Patients in the tube group used an average of 1.3 glaucoma medications vs. 0.5 medications in the trabeculectomy group (P < .001), according to the study authors.

Rates of intraoperative complications were also similar between groups, occurring in 7% of the tube group and 10% of the trabeculectomy group (P = .59). Common complications included conjunctival buttonhole, hyphema and scleral perforation, the authors said in a second study published in the same journal issue.

Postoperative complications developed in significantly more trabeculectomy patients: 57% vs. 34% of tube-treated patients (P = .001). Such complications included choroidal effusion, a flat anterior chamber and wound leakage.

Choroidal effusion was also identified as an independent risk factor for vision loss, and wound leakage was independently associated with the risk of surgical failure, the authors noted.

Overall, surgical complications that led to a second operation or loss of two or more lines of visual acuity "occurred with similar frequency with both surgical procedures," they said.