The latest innovation to combat primary open-angle glaucoma (POAG), the XEN Gel Stent, won FDA approval last November. Developed by AqueSys and later acquired by Allergan Inc., the device is aimed at decreasing IOP in patients with POAG who have not responded to, or cannot tolerate, other treatments. Canadian ophthalmologists have gotten a jump on their American counterparts in using the technology, since it was approved for use in Canada in February 2015; read on for their experiences with the new stent.

FIRST: A NICHE OF ITS OWN

The XEN differs from other stents in that it is composed of a gelatin, notes Miriam Kenrick, senior director, International Strategic Marketing - Glaucoma at Allergan. “So the body does not recognize it as foreign. As a result, you do not get an inflammatory response [to it],” she explains.

Ms. Kenrick cites other clinical benefits to the XEN as well. One is that its implantation does not preclude the potential for a trabeculectomy in the future should a patient require more invasive surgery down the road.

Another: Placement does not disrupt the conjunctiva. In fact, she says the XEN relies on the subconjunctival space for filtration of aqueous humour to decrease IOP.

Arsham Sheybani, MD, assistant professor of ophthalmology, Washington University School of Medicine in St. Louis, Mo., who implanted the gelatin stent as a fellow while working in Canada, agrees, noting that the novel aspect of the device is that it spares conjunctival tissue. “Unlike with a tube shunt or trabeculectomy, you do not damage as much conjunctival tissue when used off-label without a conjunctival incision,” he says.

And because placement of the XEN involves a minimally invasive technique, the risk of infections is minimized, Ms. Kenrick says.

Iqbal Ahmed, MD, FRCPC, assistant professor at the University of Toronto and Research Fellowship director, Department of Ophthalmology, University of Toronto in Toronto, Canada, was one of the first ophthalmologists in North America to use the ab interno gelatin stent. He notes another advantage: “[The XEN] does not require cataract surgery [in addition] to help with [intraocular)] pressure control.”

THE XEN PATIENT

Patients who represent the right fit for the XEN are those who have more severe disease or who are on multiple medical therapies to control their IOP, according to Dr. Ahmed. “We have found for patients with more significant disease (glaucoma) or patients who are on more medications pre-operatively, other procedures do not offer enough [IOP reduction],” explains Dr. Ahmed. “This is where XEN has a role.”

At the same time, Dr. Sheybani notes the XEN’s design restricts the potential for very low IOP.

“At normal aqueous humor production, the pressure should not drop below 5 mmHg,” he says.

While an additional injection of Mitomycin-C with the XEN is off-label, Dr. Ahmed has found its adjunctive use when implanting the stent produces optimal patient outcomes. He uses it routinely.

“We have found that it helps in slowing down the healing process and lowering the [intraocular] pressure around the implant,” Dr. Ahmed explains. “The pressure can go up right after surgery.”

He says appropriate use of Mitomycin-C reduces risks associated with it. “We inject a small amount to a certain location [posteriorly]. We get posterior drainage, and that mitigates the risk with Mitomycin-C. We have found it to be quite safe when used in the right way,” Dr. Ahmed says.

THE OUTCOMES ANGLE

The patient outcomes that Dr. Ahmed has recorded with the ab interno gelatin stent are consistent with those recorded in the Apex trial, a two-year prospective, multi-site, non-randomized study evaluating the gelatin glaucoma implant that was conducted in multiple countries.

Dr. Ahmed has observed in close to 50 patients who had a mean pre-operative IOP of 21.4 mmHg that the mean IOP fell to 13.1 mmHg after one year — a decrease of 36%. The mean number of pre-operative glaucoma medications was 3.6 in the same group of patients and fell to 0.9 medications at one year.

He also found that the XEN gel stent offers a very favorable safety profile. In the same dataset, four eyes, or 7% of the total, required re-operation. Bleb needling was required in 18 eyes, or 30% of the total.

Sebastien Gagné MD, FRCPC, in Boisbriand, Quebec, Canada, medical director at Institut de l’Oeil de Laurentides, and assistant professor of ophthalmology at the University of Montreal, echoed the views of his colleagues about the gelatin stent’s ability to significantly reduce IOP and medication use among patients.

“We do see a decrease in [intraocular] pressure [to the low teens] and decrease in medication use,” said Dr. Gagné, who started using the XEN in May 2016. “There is also very little time spent in the OR [to place the stent]. It is comparable to the gold standard, trabeculectomy, in terms of results.” OM

Dr. Ahmed is an investigator and consultant for Allergan. Dr. Sheybani is a consultant for Allergan. Dr. Gagné is a consultant and investigator for Allergan.