Trabeculectomy more successful than tube shunt in Primary TVT study

CHICAGO —Trabeculectomy with mitomycin C had a higher success rate than tube shunt surgery in patients with uncontrolled glaucoma and no prior incisional ocular surgery, according to 1-year results of the Primary Tube vs. Trabeculectomy study presented here.

The PTVT is a multicenter randomized clinical trial comparing the safety and efficacy of tube shunt implantation with the 350-mm² Baerveldt glaucoma implant vs. trabeculectomy with 0.4 mg/mL MMC.

Greater IOP reduction with the use of fewer glaucoma medications was observed following trabeculectomy with MMC compared with tube shunt placement during the first year, Steven Gedde, MD, told colleagues at the American Academy of Ophthalmology meeting.

“Significantly lower pressures were observed in the trabeculectomy group compared with the tube group at all follow-up points during the first year of the study,” Gedde said, adding that the greater degree of pressure reduction was achieved with fewer glaucoma medications (P < .001 at 1 week, 1 month, 3 months, 6 months and 1 year for both measures).

In the study, 117 patients completed their 1-year of follow-up visits in the tube group, and 108 patients completed their first year of follow-up in the trabeculectomy group. Demographically, average age of patients was about 62 years, about two-thirds of patients were men, and about 50% were African-American. Mean IOP at baseline was about 23 mm Hg on about three medications in both groups.

Overwhelmingly, patients had primary open-angle glaucoma, Gedde said, and average mean deviation at baseline was about –14 dB.

“There were no significant differences in any of the demographic or baseline ocular characteristics between the tube and trabeculectomy groups, indicating the randomization was very effective in creating two balanced treatment groups,” Gedde said.

There was a statistically significant difference in failure rates between the groups, 20% for the tube group and 8% for the trabeculectomy group (P = .016). The rest of the cases were considered either complete or qualified successes. Fifty-nine percent of trabeculectomy procedures were complete successes compared with 14% in the tube group (P < .001).

“The benefit of any glaucoma procedure reducing intraocular pressure really needs to be weighed against its adverse events,” Gedde said.

Surgical complications were common in the PTVT study, but most were transient and self-limited, fellow study author Sheng Lim, MD, reported in a subsequent presentation.

Postoperative interventions were performed with similar frequency after trabeculectomy with MMC and tube shunt surgery, and there were no significant differences in the rates of intraoperative complications, late postoperative complications or serious complications between the two groups, he said.

“However, the rates of early postoperative complications and early reoperation for complications were higher after trabeculectomy compared with tube shunt surgery,” Lim said.

In discussion following the presentations, Gedde commented on the differences between this PTVT study and the original TVT study, which was similar but enrolled a different population of patients:

“There are a lot of similarities between the two studies. They both enrolled patients with medically uncontrolled glaucoma randomized to a 350 Baerveldt or trabeculectomy with mitomycin C, although a lower dosage of mitomycin C in the PTVT study compared with the TVT study. ... A major difference in the study population was the fact that people in the PTVT had no previous ocular surgery and all the patients in the TVT study did have prior ocular surgery. ... The biggest difference is in success rates. In TVT, tube shunts have a higher success rate and in the Primary TVT study, trabeculectomy had a higher success rate.” – by Patricia Nale, ELS

References:

Gedde S. Treatment outcomes in the Primary Tube Versus Trabeculectomy (PTVT) study after 1 year of follow-up. Presented at: American Academy of Ophthalmology annual meeting; Oct. 14-18, 2016; Chicago.

Lim S. Postoperative complications in the Primary Tube Versus Trabeculectomy (PTVT) study during the first year of follow-up. Presented at: American Academy of Ophthalmology annual meeting; Oct. 14-18, 2016; Chicago.

Disclosures: Gedde and Lim report no relevant financial disclosures. The study was supported by grants from Abbott Medical Optics, National Eye Institute and Research to Prevent Blindness.