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Optimizing continued from page 85 Dr. Gedde said, the trabeculectomy group had lower mean IOP than the tube group. But from that point for- ward through 5 years of follow-up, mean IOP for the two groups was similar. "In terms of success or failure based on the pre-specified criteria, the 5-year cumulative probability of failure was 46.9% in the trabeculec- tomy group versus 29.8% in the tube group," he said. "We recognize that some might not consider IOP below 21 mm Hg an adequate definition of success," Dr. Gedde said, "so we conducted a post hoc analysis looking at IOP below 17 mm Hg as an additional criterion for success." In that analy- sis, the 5-year failure rates were quite similar: 54% for trabeculectomy and 32% for tube shunts. "The majority of the failures were for inadequate IOP reduction," he explained, "and hypotony and loss of light perception were uncom- mon. Also, there were a substantial number of reoperations, including eight in the Baerveldt group and 18 in the trabeculectomy group." TVT safety Efficacy is important, but what about safety? "The benefit of any procedure for lowering IOP has to be inter- preted in the context of its adverse events," said Jamie Brandt, M.D., University of California-Davis. "In TVT, complications were captured on a standardized form that allowed recording of both solicited and un- solicited adverse events." "There were a substantial num- ber of complications in TVT," said Dr. Brandt, "but most of them were transient and self-limiting." Within the first month follow- ing surgery, there were more adverse events in eyes undergoing tra- beculectomy than tube implanta- tion, said Dr. Brandt. "These included events typical to tra- beculectomy, such as shallow ante- rior chamber and wound leaks." Late post-op complications were similar in frequency between groups, he said, as were serious adverse events. Vision loss (two or more lines of acuity) occurred in 31% of patients in the tube group versus 33% in the trabeculectomy group. Among pha- kic patients, 80% in the tube group versus 79% in the trabeculectomy group experienced progressive lens opacification. TVT cost analysis A post hoc analysis was conducted to establish the relative costs associ- ated with these two procedures. "The cost of initial surgical treatment was $3,513 and $2,691 for the tube and trabeculectomy groups, respectively," said Pratap Challa, M.D., Duke University, Durham, N.C. "The average per-patient costs associated with procedures to man- age post-operative complications were $1,183 versus $431 in the tube and trabeculectomy groups, respec- tively. Accounting for the costs of re- operations, the average reoperation cost per subject was $213 in the tube group and $615 in the trabeculec- tomy group." Also, because the tube group re- quired more post-op medications than the trabeculectomy group to achieve adequate IOP control, the average per-patient monthly cost of medications was $36 in the tube group and only $20 in the tra- beculectomy group, he said. Clinical implications "Tube shunt surgery had a higher success rate than trabeculectomy with mitomycin C after 5 years in the TVT Study," Dr. Gedde said. "Both tube shunts and trabeculec- tomy with mitomycin C are good options for managing glaucoma in patients with prior cataract and/or glaucoma surgery." "The rates of late and serious ad- verse events were similar for both surgical procedures," said Dr. Brandt, "but there were more early post-op- erative complications in the tra- beculectomy group." "Tube-shunt surgery was more expensive than trabeculectomy with mitomycin C during the first 5 years of follow-up in the TVT Study," said Dr. Challa. Because the subjects enrolled in the TVT Study were somewhat het- erogeneous, with approximately half having had only prior cataract sur- gery and the other half having un- dergone prior failed trabeculectomy, the study is of limited value in deter- mining which is the best first opera- tion for patients with open-angle glaucoma. "This study has given us both the scientific and ethical basis for proceeding with the primary TVT Study, which is enrolling subjects now," said Dr. Brandt. EW Editors' note: The doctors mentioned have no financial interests related to their comments. Contact information Brandt: jbrandt@ucdavis.edu Challa: chall001@mc.duke.edu Gedde: sgedde@med.miami.edu October 2011 84-88 Glaucoma_EW October 2011-DL2_Layout 1 9/29/11 4:10 PM Page 86

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