Complete Success Rate Not as High as Expected With Gel Stent Implant for Glaucoma

While the Xen 45 gel stent implant showed beneficial long-term outcomes for the treatment of open-angle glaucoma, a substantial proportion of patients needed follow-up operations or bleb needling, according to a real-world retrospective analysis of data from an observational registry.

At 24 months, the rate of complete success — defined as an intraocular pressure (IOP) reduction ≥20% from preoperative and an IOP ≤18 mm Hg and ≥6 mm Hg with no secondary procedure at 2 years and without IOP-lowering medications — was 26%, while the rate of qualified success — defined similarly, but allowing the use of IOP-lowering medications — was 48%, reported Louis Arnould, MD, PhD, of Centre Hospitalier Universitaire de Dijon in France, and colleagues.

A secondary procedure was needed in 18% of patients, and bleb needling was performed in 28.4%, they wrote in the British Journal of Ophthalmology.

“The success rates of surgery were probably not as high as we had expected,” co-author Mitchell Lawlor, PhD, of Sydney Eye Hospital and the Save Sight Institute in Sydney, Australia, told MedPage Today.

The authors noted that other studies have reported higher rates of bleb needling at 41% to 62%, while the rate of re-operations at 24 months was similar to findings from other studies at 12 months.

Of note, the study showed worse outcomes with Xen 45 gel stent implantation combined with cataract surgery. Complete success and qualified success rates were higher in the Xen 45-alone group (33% and 52%, respectively) compared with the combined cataract surgery group (16% and 42%, respectively).

“There may be occasions where it is necessary to combine surgery, but clinicians should be aware that the probability of success is significantly reduced,” Lawlor said.

As he explained, laser therapy and eye drops are first-line therapies for open-angle glaucoma, followed by trans-trabecular glaucoma devices, often in conjunction with cataract surgery if needed. Filtration surgery is a third-line treatment for patients who need a large amount of pressure reduction or who haven’t responded adequately.

“Traditionally, filtration surgery has meant trabeculectomy or tube shunt surgery,” he said. “The most common potential complication with filtration surgery is hypotony. This can lead to vision loss. Newer devices such as the Xen stent and the PreserFlo Micro-Shunt have been developed aiming to reduce the rate of complications such as this.”

The 6-mm-long Xen 45 stent, a microtube made of gelatin, “allows fluid to pass from inside the eye to the external subconjunctival space,” Lawlor said. “It has a fixed lumen size that acts as a flow restriction.”

The alternative is to manually cut a trapdoor in the sclera, he added, but “the amount of fluid that flows through is inherently less predictable.”

Initial trials for the Xen 45 gel stent implant weren’t randomized, so it’s especially important to gather real-world data, he noted.

“Glaucoma surgery outcomes notoriously vary wildly depending on how the researchers decide to define success,” he said. This study follows the recommendations of the World Glaucoma Association in regard to how it defines successful procedures.

Leo Seibold, MD, of the University of Colorado School of Medicine in Aurora, told MedPage Today that the new research “provides nice insight about real-world outcomes,” but he was surprised by the “relatively low success rates overall.”

“Their complete and qualified success rates were at 50% or much less depending on the IOP criteria used at 24 months,” he said. “The final IOP was only in the mid-teens as well, and they also reported a relatively high rate of vision loss and need for further surgery. … Patients with IOP goals in the mid-teens or higher would be more appropriate candidates.”

The study seems valid, he added, although “its retrospective design limits the overall confidence in the results.”

He also pointed out that “the finding of worse outcomes when combined with cataract surgery is a novel finding and should guide surgeons away from combining Xen surgery with cataract surgery whenever practical.”

For this study, the researchers identified a baseline cohort of 638 eyes among adult patients from the international Fight Glaucoma Blindness registry. All had ocular hypertension or open-angle glaucoma, and those who’d previously undergone glaucoma filtration surgery were excluded.

Of the patients, 69% had primary open-angle glaucoma, 51% were men, and mean age was 72.4 years. Mean preoperative IOP was 21.4 mm Hg, mean number of medications was 2.7, and the average visual field mean deviation where that was recorded was -10.2 dB.

At 24-month follow-up, IOP was 16.8 mm Hg (a mean reduction of 21.7%) on 1.2 IOP-lowering medications.

Arnould and team noted that study limitations included the mostly white population (percentage not provided), the lack of treatment standardization, and the high proportion of patients with primary open-angle glaucoma.