BEST PROCEDURE AFTER TRABECULECTOMY FAILURE

Glaucoma surgeons are often faced with the question of the best procedure to perform when the initial trabeculectomy has failed. Should they repeat the trabeculectomy or opt instead to place a tube shunt?

Two leading glaucoma specialists, Robert D Fechtner MD and Richard K Parrish MD, presented arguments in favour of each approach at a head-to-head debate at the World Glaucoma Congress.

Acknowledging that the “best advice is not to have the first trabeculectomy failâ€, Dr Fechtner, professor of ophthalmology at the Institute of Ophthalmology and Visual Science, New Jersey Medical School, said that when failure does occur the surgeon should keep his options open and not routinely dismiss the possibility of a second trabeculectomy. “Tubes and shunts are not without their own problems. Why do a repeat trabeculectomy? Because it is a simple, efficient, and effective procedure that can be successful with careful patient selection,†he said.

A key consideration is to obtain an understanding of why the initial trabeculectomy surgery failed, said Dr Fechtner. “The reality is that you cannot answer what procedure to do next if you do not understand the procedure that was done previously. Trabeculectomies fail for a number of reasons, perhaps because of poor patient selection, by operating on patients who should not have had a trabeculectomy in the first place, and also because of intraoperative complications with the conjunctiva, the sclera, the vitreous, and with bleeding,†he said.

Above all, initial trabeculectomy failure is often directly related to postoperative wound healing response, said Dr Fechtner.

Dr Fechtner said that the evidence from the scientific literature is far from conclusive concerning repeat glaucoma surgery.

“There are limited head-to-head comparisons with modern surgical techniques and many of the studies have inappropriate patient populations for us to truly gauge whether trabeculectomy or tube might be the best option,†he said.

Referring to the Trabeculectomy versus Tube (TVT) study, Dr Fechtner said that while the results have clarified some questions relating to surgical treatment, many others remain unanswered.

Summing up, Dr Fechtner said surgeons could and should consider repeat trabeculectomy if they adhere to rigorous patient selection.

Making the case for tube shunt surgery as the appropriate second procedure following initial trabeculectomy failure, Dr Parrish MD, professor of ophthalmology at the Bascom Palmer Eye Institute, Miami, Florida, US, said his argument was based on an evidence-based review of the medical literature and recent clinical trial data.

He cited the Cochrane Collaboration by Don Minckler et al, a meta-analysis of 15 trials involving 1,153 participants with varied diagnoses of glaucoma, which found insufficient evidence to conclude that clinical outcomes of trabeculectomy differ substantially from those of aqueous shunts in similar patients with complicated glaucomas. The review also said that there was insufficient evidence to conclude that any specific aqueous shunt is superior to the others currently in widespread use.

An ophthalmology technology assessment published in Ophthalmology in 2008 concluded that aqueous shunts seem to have benefits in terms of IOP control and duration of benefit comparable with those of trabeculectomy in the management of complex glaucoma in aphakic or pseudophakic eyes after prior failed trabeculectomies, said Dr Parrish.

The five-year follow-up data from the TVT study also showed that tube shunt surgery has a higher success rate than trabeculectomy with mitomycin C. Moreover, a higher rate of reoperation was observed after trabeculectomy with mitomycin compared with tube shunt surgery.

Of those patients who failed their initial surgery, whether primary trabeculectomy or drainage implant, the choice made by the surgeon for subsequent treatment tells its own story, said Dr Parrish. “The surgeons voted with their decision making. Of the 18 failures in the trabeculectomy group, 15 of those patients underwent subsequent tube shunt surgery. Of the eight failures in the tube group, four had another tube shunt procedure and four had transscleral cyclophotocoagulation,†he said.