Data on tube shunts emerging as procedure popularity continues to grow

Although trabeculectomy remains the gold standard for glaucoma surgery, the number of procedures has been declining steadily over the past decade, whereas the number of tube shunt placements has quadrupled, said Sameer Ahmad, MD, assistant professor of ophthalmology, The Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore.

Dr. Ahmad said there is a paucity of prospective data comparing trabeculectomy with tube shunts. Recently reported 1-year data from the multicenter, randomized Tube Versus Trabeculectomy study comparing the 350 mm² glaucoma implant (Baerveldt, Advanced Medical Optics) with trabeculectomy is encouraging for the tube procedure, he said. Results showed mean IOP was comparable in the two study groups. Patients who received tube shunts used slightly, but significantly more medications on average, and they also had a significantly lower rate of failure. Complications also were relatively similar in the two groups, especially in terms of rates of choroidal effusion and shallow chambers, although there were fewer corneal problems with trabeculectomy.

Additional information on the complications of tube shunt surgery is being provided by an ongoing retrospective study underway at Duke University. Data from nearly 1,300 shunts placed between 2002 and 2006 showed about 8% needed surgical revision. Tube occlusion was the most common reason for going back to the operating room and it occurred in 3.3% of eyes, he said.

"There are four things that cause tube occlusion: vitreous, fibrin, iris, or blood," Dr. Ahmad said. "As with most things surgically, the key is prevention."