Viscoelastic injection may improve microstent efficacy

Take-home message: Patients receiving a sodium hyaluronate ophthalmic viscoelastic device injection showed a trend toward greater reduction in IOP than patients who received a microstent alone.

Reviewed by Ernesto Calvo, MD

Panama City-Injecting sodium hyaluronate ophthalmic viscoelastic device (OVD) prior to placement of a microstent in the supraciliary space may result in lower IOP, said Ernesto Calvo, MD.

“We’re really excited about this new technique,” said Dr. Calvo, an ophthalmologist practicing in Panama City, Panama. “I’m using it here in my daily glaucoma treatment routine-it’s working great.”

In a study, Dr. Calvo and colleagues injected the OVD (Healon 5, Abbott Medical Optics) through a guide wire tube before deploying a microinvasive glaucoma surgery stent (CyPass Micro-Stent, Alcon Laboratories/Transcend Medical).

Patients receiving the OVD showed a trend toward greater reduction in IOP than patients who received the microstent alone. Though the difference was not statistically significant, it provided evidence to justify a larger study, Dr. Calvo said.

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Designed to reduce IOP by enhancing aqueous outflow to the suprachoroidal space, the stent is implanted between the sclera and the ciliary body, via an ab interno, clear corneal incision. It does not penetrate the sclera. The trabecular meshwork integrity is preserved.

Regulatory agencies have approved the device for sale in Europe and Panama among other countries, and the FDA is reviewing an application for sales in the United States.

Aqueous lakes

In using the stent, Dr. Calvo and colleagues observed through optical coherence tomography (OCT) and ultrasound biomicroscopy that some patients had aqueous lakes or tenting posterior to and around the microstent.

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“The more the lake and the more the tenting, the more the decrease in pressure in the patients,” Dr. Calvo said.

Researchers hypothesized that the larger peristent supraciliary space enhanced fluid outflow, lowering IOP and reducing the need for glaucoma medication.

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They decided to try expanding the supraciliary reservoir by injecting OVD through the guide wire tube during microstent placement.

Sixty-three subjects with primary open-angle glaucoma, a mean age of 68 years, a Shaffer classification grade of 3-4, and an unmedicated IOP of 21 to 36 mm Hg were enrolled.

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Patients were divided into three groups of 21 each. One group received the microstent without a sodium hyaluronate injection, one received the microstent with an injection of 30 µl of sodium hyaluronate, and one received the microstent with an injection of 60 µl.

Follow-up at 1 year

Follow-up at 1 year

At 12-months follow-up, researchers measured larger drainage reservoirs in patients receiving OVD than in those who received only the microstent. Those who received 30 µl were 2.47 times larger, and those who received 60 µl were 3.21 times larger.

All the groups in the study needed less medication 12 months after placement of the microstents. Almost half the patients needed no medication at all. However, there was no significant difference among the groups.

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Those patients who received the microstent alone showed an average reduction of 7 mm Hg in IOP 12 months after the procedure. Those injected with 30 µl of sodium hyaluronate showed a reduction of 8.7 mm Hg, and those injected with 60 µl of sodium hyaluronate showed a reduction of 9.8 mm Hg.

These differences among the groups were not statistically significant, perhaps because not enough patients were enrolled in each group, Dr. Calvo said.

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Still, he speculated that the OVD might reduce inflammation and scarring as well as preserving a larger aqueous lake.

“We don’t know exactly how it’s working,” he said. “That’s something we have to study a bit more.”

None of the patients in any group experienced a serious or vision-threatening adverse event due to treatment. There were no retinal detachments, no anterior chamber or vitreal hemorrhage, and no persistent inflammation. There were no significant differences among the three groups.

Ernesto Calvo, MD

E: ecalvo86@mac.com

This article was adapted from Dr. Calvo’s presentation at the 2015 meeting of the American Academy of Ophthalmology. Dr. Calvo reported that he has research funding from Transcend Medical.