Tube shunt surgery more successful than trabeculectomy with MMC, study shows

DANA POINT, Calif. — Tube shunt surgery had a higher success rate than trabeculectomy with mitomycin C after 5 years of follow-up in the Tube Versus Trabeculectomy Study, a researcher reported here.

At 5 years, both procedures were associated with similar IOP reduction and use of supplemental medical therapy, but there was a higher rate of reoperation for glaucoma after trabeculectomy with MMC, Steven J. Gedde, MD, said at the American Glaucoma Society meeting.

The TVT Study compares the safety and efficacy of tube shunt surgery with trabeculectomy with MMC in patients with previous ocular surgery. Outcome measures include IOP, visual acuity, visual field, quality of life, reoperations, complications and the need for supplemental medical therapy.

The study enrolled 212 patients, 107 in the tube shunt group and 105 in the trabeculectomy group.

At baseline, mean IOP was approximately 25 mm Hg on an average of three medications. A majority of patients had primary open-angle glaucoma, and the average mean deviation was roughly -16 decibels, Dr. Gedde said.

"There were no significant differences in any of the baseline ocular or demographic characteristics between the tube group and the trabeculectomy group, suggesting that randomization was very effective in creating balanced treatment groups," he said.

The cumulative probability of failure at 5 years was 46.9% in the trabeculectomy group and 29.8% in the tube group, a statistically significant difference.

"In my opinion, tube shunt surgery and trabeculectomy with mitomycin C are good options for managing glaucoma in patients with prior cataract and glaucoma surgery. This [opinion] seems to be supported by the TVT Study," Dr. Gedde said.

However, when selecting a glaucoma surgical procedure, multiple factors must be considered, including efficacy, risk of complications, and the surgeon's skill and experience with the procedure, he said.

"The benefit of any glaucoma procedure in reducing pressure must be interpreted in the context of its adverse events," Dr. Gedde said.

• Disclosure: Dr. Gedde reports no financial interests in the subject matter of the study.

The investigators have challenged the standard algorithm of performing trabeculectomy before seton surgery (tube surgery) and suggest that seton surgery may be considered earlier in the treatment of surgical glaucoma. The advantages of a seton over trabeculectomy include fewer postoperative visits, less risk of long-term endophthalmitis, and less need for postoperative procedures such as 5-fluorouracil injections, bleb needling and suture removal.

The disadvantages of seton surgery include tube and plate exposure, strabismus, higher intraocular pressures and increased risk of corneal endothelial loss and edema. Finally, the ophthalmologist has fewer subsequent options for uncontrolled IOP with seton surgery first.

Future studies should include measurement of corneal endothelial cell density and whether any demographic or clinical characteristics differentiate between the procedures. For example, perhaps elderly patients do better with trabeculectomy. Or perhaps patients with early glaucoma do better with seton surgery. I look forward to future results.

– Steven L. Mansberger, MD, MPH
Devers Eye Institute, Portland, Ore.
Disclosure: Dr. Mansberger reports no financial disclosures relevant to this presentation.