Combined Glaucoma + Cataract Surgery as Effective as Separate

Richard Mark Kirkner

October 04, 2022

CHICAGO, Illinois — A large retrospective analysis of more than 150,000 eyes from a national eye registry have shown that combining surgeries for glaucoma and cataract into one procedure didn't diminish the effectiveness of the glaucoma portion. Moreover, people who had two separate operations were more likely to need another glaucoma procedure.

The retrospective study, presented as a poster at the annual meeting of the American Academy of Ophthalmology here in Chicago, analyzed data on 153,354 eyes, 35,657 of which had the combined procedures, from the Intelligent Research in Sight (IRIS) registry, a national patient database maintained by the American Academy of Ophthalmology. The remainder of the eyes had only glaucoma surgery, which either consisted of either a trabeculectomy or implantation of a glaucoma drainage device (GDD).

Trabeculectomy and GDD both aim to relieve pressure in the eye by creating channels for drainage of fluid within the eye, known as the aqueous humor. The former involves removing part of the trabecular meshwork at the front of the eye. The latter uses a shunt to drain the fluid.

Dr Nazlee Zebardast

Over the past decade or so, the trend has been to perform these glaucoma procedures during cataract surgery. Senior study author Nazlee Zebardast, MD, MSc, director of glaucoma imaging at Massachusetts Eye and Ear in Boston, told Medscape Medical News that smaller studies have suggested that combining glaucoma surgery, especially trabeculectomy, with cataract surgery seemed to diminish the effectiveness of the glaucoma portion, but that limited work had been done evaluating the combination of GDD and cataract surgery, which involves phacoemulsification.

"We found that overall reoperation rates were low for all groups, but that the surgery when combined with phacoemulsification actually had a lower reoperation rate than the surgery done standalone, and that was also in line with what other studies have done," Zebardast said.

The researchers divided the study population into four treatment groups: trabeculectomy alone (n = 66,939) or in combination with cataract surgery (n = 28,985); and GDD alone (n = 50,758) and with cataract surgery (n = 6672).

In presenting the results, Elizabeth Ciociola, a student at the University of North Carolina School of Medicine, reported that of the patients receiving a standalone trabeculectomy or those receiving combined trabeculectomy-cataract surgery, 12.7% vs 8.6% needed a second operation for the glaucoma portion within 3 years of the index procedure. This was compared with 8.8% vs 6.3% for GDD alone and in combination (P < .001).

Said Zebardast, "But we did find that intraocular pressure [IOP] declined to a greater amount when both trabeculectomy and drainage devices were done alone without phacoemulsification." IOP declined from an average of 22 mm Hg at baseline to 13 mm Hg at 3 years for trabeculectomy alone vs 19 mm Hg to 14 mm Hg in the trabeculectomy-phacoemulsification group. In the GDD-only and combined groups, the IOP declines were from 26 mm Hg to 15 mm Hg and 23 mm Hg to 15 mm Hg, respectively.

Visual acuity improved slightly in patients who had the combined procedures and deteriorated slightly in those who had standalone procedures, varying only by 0.2 rows on the LogMAR chart either way.

Risk Factors for Later Surgery

The study also looked at risks factors for having another glaucoma surgery within 3 years. "We found that a lot of demographic factors as well as ocular factors predicted higher rates of failure," Zebardast said. "Non-Hispanic Black race and Hispanic/Latino race predicted higher rates of failure among the trabeculectomy group. We also found that higher severity of glaucoma and higher intraocular pressure at baseline had a higher risk of failure."

Non-Hispanic Black patients had almost twice the likelihood of reoperation with either trabeculectomy approach and a 20% to 24% risk with either GDD procedure. Patients with secondary, moderate, or severe glaucoma also had higher risks with all four procedures, with failure rates almost tripled for GDD-cataract surgery in moderate glaucoma, and both combined operations in severe glaucoma.

"We looked at complication rates in all groups and we found that overall complications were very rare," Zebardast said. Ocular complication rates within 3 months of either trabeculectomy or GDD were 1% and 2.2%.

Strengths and Limitations

The study population size is one of the study strengths, Zebardast noted. "Just the size of our study and the longitudinal aspect of it is unprecedented," she said. But she also noted limitations using registry data, namely the lack of verifiable, detailed examination information. She also noted that IRIS itself "oversamples from community practices vs academic settings."

Dr Arsham Sheybani

"This study solidifies some of what we already have seen demonstrated in more robust studies with less missing data," Arsham Sheybani, MD, a glaucoma specialist at Washington University, St. Louis, Missouri, said in an interview. "However, this is still one of the larger real-world datasets that looks at phaco combined with subconjunctival surgery vs those surgeries alone."

He also noted a number of limitations using the IRIS registry data, including missing information about previous surgeries and what IOP-lowering medications the patients may have been on. "The design is appropriate," he said. "However, results will be confounded by what types of surgeries patients had received prior to their index surgery. Acquiring data 2 years prior to the index surgery would at least ensure if there were any operations within 2 years of the index surgery."

Research to Prevent Blindness funded the study. Sheybani disclosed relationships with Allergan/AbbVie, Ivantis, New World Medical, and Santen. Ciociola and Zebardast have disclosed no relevant financial relationships.

American Academy of Ophthalmology: Poster #124: Presented September 29, 2022.

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

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