Trabeculectomy remains the most commonly performed surgical glaucoma procedure. However, interest in identifying alternatives involving simpler postoperative follow-up and a better safety profile is fueling the development of newer surgical procedures.
"A 2007 publication analyzing Medicare beneficiary data reported that in 2004, trabeculectomy was performed more often than shunt surgery by a ratio of 4.6:1. However, the numbers of trabeculectomy alternative procedures being performed, particularly glaucoma tube shunt surgery, have been increasing dramatically," observed Dr. Smit, clinical instructor, department of ophthalmology, University of Washington, Seattle, and in private practice, Spokane Eye Clinic, Spokane, WA.
Treatment of choice
"Results of randomized clinical trials have provided us with benchmarks for achieving IOP control," Dr. Smit said. "The Early Manifest Glaucoma Trial showed that the risk of primary open-angle glaucoma progression decreased by 10% for each 1 mm Hg in IOP, and in the Advanced Glaucoma Intervention Study, patients whose IOP was kept below 18 mm Hg at 100% of follow-up visits over a 6-year period benefited with no visual field loss. These data provide an incentive to choose a procedure that we know will lower IOP, and by and large, we know that can be accomplished with trabeculectomy."
Recent data from the Tube Versus Trabeculectomy Study also provide a rationale for favoring trabeculectomy. Although there were more failures in the trabeculectomy group, the results for complete successes, i.e., IOP control without medication, favored trabeculectomy.
"In my experience, many of the patients who come to be surgical candidates are intolerant of medications or cannot use them for some other reason. In this situation, offering a procedure that I expect will require adjunctive medical therapy is not satisfactory," said Dr. Smit.
Paucity of data from prospective, randomized, head-to-head comparison trials evaluating the various newer glaucoma surgical procedures-including canaloplasty, trabeculectomy ab interno (Trabectome, Neomedix), newer shunts, and endoscopic cyclophotocoagulation-also limits assessment of their role relative to trabeculectomy.
Follow-up a problem
However, the need for intensive postoperative follow-up after trabeculectomy and the risk of a number of early and late complications are fueling a search for other options.
"Getting through the time in the OR is the easy part of trabeculectomy. It is the many patient visits and complications that have to be managed after surgery that are a frustrating challenge," Dr. Smit said.
In the Collaborative Intervention Glaucoma Treatment Study, early complications after trabeculectomy were reported in 50% of patients. These events included shallow or flat anterior chamber, encapsulated blebs, ptosis, serous choroidal detachment, and hyphema. Long-term complications include the most dreaded of all, endophthalmitis, along with bleb failure, bleb leaks, late hypotony, bleb dysesthesias, and cataract.
"I have seen more patients completely lose vision or an eye to bleb-related endophthalmitis than any other condition," said Dr. Smit.
Procedural modifications are being introduced with the hope of improving the safety profile of trabeculectomy. However, the risk of endophthalmitis has not been eliminated, and ultimately, a procedure that does not leave an eye with a hole is being sought as a better alternative to trabeculectomy.