The risk for endophthalmitis in patients with glaucoma who undergo drainage procedures appears to persist for at least 5 years after the initial operation, a new research showed.

The findings, from one of the largest studies to look at the question, showed the two main procedures for glaucoma drainage — device surgery and trabeculectomy — carry roughly the same risk for eye infection. However, drainage surgery carries three to five times the risk for infection than does another operation that requires the placement of a medical device under the outer ocular tissue to repair a retinal detachment.

“Endophthalmitis risk after tube shunt surgery continued to accrue through 5 years, or in other words it can occur late, so surveillance and monitoring is always warranted,” Qais Dihan, MD, an ophthalmology resident at the University of Arkansas Medical School in Little Rock, Arkansas, told Medscape Medical News. Dihan reported the findings at American Glaucoma Society (AGS) 2026 Annual Meeting.

The study found the risk for endophthalmitis after glaucoma drainage device surgery, also known as tube shunt surgery, more than doubled, from 0.82% at 1 year after surgery to 1.87% at 5 years.

The study sought to quantify not only the cumulative incidence of endophthalmitis after drainage device surgery and trabeculectomy but also to compare outcomes of drainage device surgery and scleral buckle, two procedures that involve insertion of a device into the ocular surface, Dihan said.

Drainage device surgery involves the insertion of a small silicone tube in the front of the eye to allow drainage of the aqueous humor from inside the eye, hence reducing intraocular pressure, thought to be a key driver of glaucoma. In trabeculectomy, the surgeon creates a small flap to drain the aqueous humor. Both procedures involve creation of a filtering bleb, a bubble-like blister on the outside conjunctiva of the eye that collects the drained fluid and returns it to the surrounding tissues and bloodstream. Trabeculectomy does not involve insertion of a device.

Scleral buckle is an operation to repair retinal detachment. The surgeon sutures a silicone band or sponge onto the outer surface of the sclera to push the wall of the eye inward toward the detachment.

The study included 12,849 patients who had glaucoma drainage device surgery, 9006 who had trabeculectomy, and 3097 who had scleral buckle.

The demographics of the two glaucoma surgery groups were similar, but the group that underwent scleral buckle procedures was younger (average age, 45 years vs 63 and 68 years for the drainage device and trabeculectomy groups, respectively). The scleral buckle group had a higher proportion of men (58.1% vs 50% for the glaucoma surgery groups) and less racial diversity (70.6% White vs 54.2% and 57.8%; and 10.72% Black vs around 25% for both glaucoma surgery groups.)

The study measured the cumulative incidence of endophthalmitis at three time points: 1 year, 3 years, and 5 years. For drainage device surgery the respective rates of endophthalmitis were 0.82%, 1.57%, and 1.87%. For trabeculectomy they were 0.47%, 0.78%, and 0.96%, respectively. For the scleral buckle group, the endophthalmitis rates were 0.19%, 0.23%, and 0.39%, respectively.

The adjusted hazard ratio between the two glaucoma surgeries did not differ significantly at the three time points, Dihan said.

However, he reported, “By taking the comparison between glaucoma drainage device surgery and scleral buckle, there was a consistently higher risk of endophthalmitis at each of our measured time points.” The adjusted hazard ratios were 4.72 at 1 year, 3.29 at 3 years, and 5.43 at 5 years, Dihan said.

This study is one of the largest evaluating the risk for endophthalmitis in glaucoma drainage device surgery and trabeculectomy, Dihan told Medscape Medical News. He cited three previous studies published by the Tube vs Trabeculectomy Study Group, ranging from 212 to 242 patients. A 2024 study using a Medicare data set of 156,105 standalone glaucoma surgeries found a 0.15% rate of endophthalmitis, Dihan noted.

The results are “especially generalizable” to the clinic, Dihan said. “Clinicians should be aware that, although uncommon, endophthalmitis represents a real, and frankly serious, complication that can occur after surgery and can present as a late-term complication years after surgery,” he said.

Mohamed Khodeiry, MD, MSc, a glaucoma specialist at the University of Louisville, in Louisville, Kentucky, said the size of the study population and “good control of covariates between cohorts” were strengths of the research. However, he said, further studies should look at how endophthalmitis in these patients affected their visual outcomes.

“The study helps characterize the nature of what may predispose to endophthalmitis when comparing trabeculectomy vs glaucoma drainage device and specifies hardware vs bleb comparisons,” Khodeiry told Medscape Medical News. “Taken together, the findings suggest that infection risk is not confined to the early postoperative window and that factors unique to glaucoma drainage device procedures likely contribute more than hardware alone.”

The primary clinical takeaway is that endophthalmitis risk persists for years after glaucoma drainage device surgery, Khodeiry said. “The results reinforce the importance of counseling patients that late infection, although rare, can occur and may present with symptoms that warrant evaluation,” he said. “Similarly, for ophthalmologists, it is our duty to be knowledgeable of this and maintain long-term care and surveillance of our patients.”

This study was independently supported. Dihan and Khodeiry reported having no relevant financial relationships.

Richard Mark Kirkner is a medical journalist based in Philadelphia.