Preserflo microshunt shows good outcomes out to 2 years in primary open-angle glaucoma

Two-year results of a multicenter European study showed that the Preserflo microshunt, an ab externo filtration surgery device, safely reduced IOP in eyes with primary open-angle glaucoma.

In 81 patients aged between 18 and 85 years who were not adequately controlled on maximal tolerated medical therapy, mean IOP decreased from 21.7 mm Hg at baseline to 14.5 mm Hg at 1 year and was stable at 2 years. Mean number of medications decreased from 2.1 at baseline to 0.5 at 2 years, with 73.8% of patients requiring no medications. No long-term sight-threatening adverse events related to the Preserflo microshunt (Santen) were reported.

“As a study investigator, I started using the microshunt 5 years ago, and I have been using it since in my daily practice,” Florent Aptel, MD, PhD, professor and head of the glaucoma and anterior segment unit at the University Hospital of Grenoble, France, told Healio/OSN. “I use it in cases of progressive glaucoma under medical and/or laser treatment and mainly in patients with primary open-angle glaucoma. I also use the stent in some forms of secondary open-angle glaucoma, such as pigmented, exfoliative or corticosteroid-induced glaucoma, and I find the results to be similar.”

MIGS categories

Microinvasive surgical devices fall into three categories, Aptel said.

Suprachoroidal stents are not currently used in practice. The CyPass micro-stent (Alcon) showed encouraging results in clinical trials, but a significant reduction in endothelial cell density occurred in the long term, leading to withdrawal of the device from the market. Other devices are in development, but long-term studies will be required to prove their safety.

Trabecular bypass stents, such as the iStent (Glaukos), are often used in combination with cataract surgery. They allow a significant drop in pressure but less than that obtained after filtration surgery, and the devices are mainly used in patients with early or moderate glaucoma with the main goal of reducing the number of glaucoma eye drops.

Together with the Xen gel stent (Allergan), the Preserflo microshunt belongs in a third category of microinvasive surgery stents, implanted ab externo to create a pathway for the aqueous humor to flow from the anterior chamber through the subconjunctival space and into a filtering bleb. The aim is to obtain pressure reduction similar to filtration surgeries but with a better tolerance profile and rapid visual recovery.

“The Preserflo microshunt differs from other devices in this class of stents by a significant drop in pressure, which is predictable, maintained over time and above all by a low rate of fibrosis of the bleb. As a result, postoperative management is simple, and needling and surgical revision procedures are not often required,” Aptel said.

Surgical procedure

Implantation of the microshunt is quick and easy with a short learning curve. The technique is standardized and reproducible, according to Aptel.

A fornix-based conjunctival flap is performed, and the underlying sclera is delaminated to a depth of approximately 8 mm. Mitomycin C is then applied with a sponge. Within this space, a shallow scleral tunnel is created, 3 mm from the limbus, and a needle is introduced and then retrieved. Through this tunnel, the microshunt is driven to reach the anterior chamber. Aqueous flow should commence at this point, and the flap is repositioned.

“Installation of the stent takes about 5 to 10 minutes and can most of the time be done under local or sub-Tenon’s anesthesia. The procedure can easily be combined with cataract surgery, but the trials so far have evaluated the microshunt as a stand-alone procedure,” Aptel said.

He performs the surgery on an outpatient basis, with a follow-up similar to that of a classic filtration surgery.

A good safety profile

The most common nonserious adverse events reported in the study were episodes of increased IOP in about a quarter of the patients, successfully treated with medications or selective laser trabeculoplasty.

“The low risk of fibrosis of the bleb and the absence of a scleral flap suture mean that procedures to manage the filtration bleb are less frequent than after trabeculectomy,” Aptel said.

In the study, needling or postsurgical injections of the bleb were performed in five patients (6.2%), and only 7.4% of patients required a reoperation by year 2. The number of bleb revisions alone (9.9%) was significantly lower compared with published data for other bleb-forming procedures such as trabeculectomy and Xen implantation. However, a direct comparison between microshunt and Xen in prospective, randomized studies has not been conducted to date.

A trend toward greater IOP reduction was found in the study in the subgroup in which 0.4 mg/mL MMC was used as compared with 0.2 mg/mL MMC. This could indicate that higher concentrations of MMC have a significant impact on mitigating fibrosis. However, because the study was not powered to assess the effects of different MMC concentrations, further investigation is needed to evaluate the potential benefits of higher concentrations.

“The results so far are very promising, and it will be interesting to evaluate several parameters and new indications in future studies,” Aptel said. “Some of these studies are already underway, and others should be carried out. We can look at an evaluation of the long-term results (3 to 5 years), the results of the combined cataract-Preserflo procedures, and the results in indications other than POAG, such as exfoliative glaucoma, pigment dispersion glaucoma, high myopia and also in angle-closure glaucoma in combination with cataract surgery. It will also be interesting to know the effect on long-term endothelial cell density. Finally, studies could assess and compare the effect of needle revisions vs. full surgical revisions.”

The Preserflo microshunt is currently available in Europe, Canada and Australia, but it has not yet received FDA approval.

For more information:

Florent Aptel, MD, PhD, can be reached at Clinique Universitaire d’Ophtalmologie, Hôpital Michallon, Chu Grenoble Alpes, CS10217 38043 Grenoble Cedex 9; email: aptel_florent@hotmail.com.