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A large international, multicenter study has shown that creating a full-circumference incision around the trabecular meshwork to lower intraocular pressure (IOP) in open-angle glaucoma, a procedure known as 360-degree trabeculotomy, reduced the need for a second operation compared with the 180-degree approach while achieving similar reductions in pressure.

The retrospective, consecutive cohort study of 177 eyes of patients with glaucoma aged 40 years and older found that 74.4% of patients in the 360-degree group and 56.3% in the 180-degree group achieved surgical success (P = .0016), Ahmed Abdelaal, MD, a research fellow at Prism Eye Institute in Oakville, Ontario, Canada, reported at the annual meeting of the American Glaucoma Society. Criteria for surgical success at 1 year of follow-up were IOP below 18 mmHg and either a reduction in pressure of more than 20% from baseline with the same number of medications or a decline in pressure with fewer medications.

Limited Reports on 360-Degree Trabeculotomy

"The current clinical literature has been limited when it comes to assessing the efficacy of full 360-degree trabeculotomy compared to lesser extents, with some demonstrating superiority of 360-degree while others reporting comparable results," Abdelaal told Medscape Medical News. "Most papers published on this topic have studied eyes that underwent concurrent cataract surgery, which is known to also reduce intraocular pressure."

The study Abdelaal reported on included only eyes that did not have concurrent cataract surgery to remove that as a confounding factor.

He reported on outcomes of 64 eyes that had the 180-degree procedure and 113 that had the 360-degree operation. A higher proportion of patients in the latter group had advanced glaucoma, 31.4% vs 25%. They were treated at seven centers in Canada, Turkey, and Japan between June 2015 and November 2021. The procedures were either ab interno suture trabeculotomy or ab interno catheter trabeculotomy with viscodilation, and participating surgeons used their own discretion in choosing the operation.

Based on a hazard ratio (HR) analysis, the 180-degree patients had more than twice the rate of operation failure, Abdelaal said (adjusted HR, 2.6).

Reductions in IOP at 1 year were comparable between the two groups, he said: From 24 to 13 mmHg on average in the 180-degree group and from 25 to 12 mmHg in the 360-degree patients.

Postoperative complications also were comparable, he reported, although the 360-degree patients had significantly higher rates of hyphema of at least 2 mm at 3 months, 21.2% vs 1%. However, beyond the 3-month mark, the rates evened out, "with diminishing significance as we reached postoperative month 12," he said.

Abdelaal noted the limitation of the retrospective study, which did not randomize eyes to the respective procedures. "We recognize the inherent limitation in confounding by an indication perspective, and it's likely that eyes receiving 360-degree had worse disease, yet our study still demonstrates a difference in efficacy favoring 360-degree trabeculotomy," he reported.

Leo Seibold, MD, a professor of ophthalmology at the University of Colorado School of Medicine in Aurora, Colorado, who was not affiliated with the new study, acknowledged the debate surrounding trabeculectomy size in glaucoma.

"This study adds to the existing literature and further supports that a bigger opening is better in terms of treatment success in lower IOP and medication requirement, but also more likely to result in postoperative hyphema," Seibold said.

The study sample size was "robust," he said, adding, "its weaknesses include its retrospective nature, nonrandomized study groups and differences in baseline characteristics between study groups."

"Clearly," Seibold added, "a prospective, randomized controlled study is needed to better compare the outcomes between 180- and 360-degree trabeculotomy."

Abdelaal had no relevant disclosures. Seibold is a consultant for New World Medical. 

Richard Mark Kirkner is a medical journalist based in the Philadelphia area.