Microshunt moves aqueous to ocular surface
A new glaucoma microshunt that drains the aqueous onto the ocular surface is advancing its way through studies.
“It is the first and only device shunting the aqueous to a location that is not the subconjunctival space, nor the conventional outflow system or the suprachoroidal space. It is a novel mechanism of action, very simple and direct, with no possible source of downstream resistance, such as episcleral venous pressure,” Patrick J. Riedel, MD, said in an interview with Ocular Surgery News.
The Beacon Aqueous Microshunt (BAM, MicroOptx), formerly the Brown Glaucoma Implant, derived from the name of its inventor, has an overall length of 3.1 mm, with an internal flow channel of 30 µm × 48 µm and an external flange of 1.7 mm. It is inserted under topical anesthesia through a small incision in the peripheral cornea, with the external flange resting on the ocular surface.
“The procedure takes less than 1 minute to perform. Flow through the channel can be seen immediately, the aqueous humor is shunted directly to the tear film, and no peripheral flow is observed,” Riedel said.
Through a combination of advanced biomaterials, microengineering and nanotechnologies, the BAM aims to overcome the problems and limitations of competing technologies in terms of both effectiveness and safety.
One major advantage is the ability to prevent retrograde migration of pathogens into the eye, which relies on the combination of two factors. One is the shear stress from the laminar flow of the aqueous.
“Aqueous flows through the channel at such a velocity that pathogens cannot adhere to the walls of the device,” Riedel said.
But even more important is the material the channel is made of, which prevents adherence.
“Polyethylene glycol is a superhydrophilic material to which bacteria cannot cling,” Riedel said.
Preclinical studies over many months have shown that no intraocular infection occurs and no pathogens are present in the aqueous even when infection is induced on the ocular surface.
In addition, the aqueous outflow constantly bathes the cornea with lubricating, nutrient-rich aqueous humor, which may be effective for treating dry eye and ocular surface disease.
“The Schirmer test shows significant increase at 6 months as compared with baseline, which has huge potential for improving tear film composition and volume. This additional benefit of the device will be evaluated in studies in addition to IOP,” Riedel said.
IOP lowering with no medications
Twenty-six patients have been implanted with this device within the first clinical studies carried out in the United States and Europe, and at least half of them have reached 1 year of follow-up.
Mean IOP at 6 months was 13 mm Hg without medications as compared with 27 mm Hg at baseline with medications. A greater than 20% reduction of IOP at the last visit was achieved by 87% of patients, with complete elimination of the need for medications in nearly all patients. The majority of patients found the device extremely comfortable and said they were satisfied or extremely satisfied.
No sight-threatening complications, no infections, no uveitis, no dislocations and no device migration occurred. In six eyes, device blockage occurred in the early postoperative period for reasons that have not yet been clarified. All cases but one resolved completely with minimal or no manipulation or with intervention such as YAG laser. One patient in the European cohort had the device explanted due to persistent blockage. Two patients reported mild irritation.
“Our hope is that we will continue to see these good outcomes and excellent safety profile with no infection in the long term. Meanwhile, the design is undergoing further improvements. The new prototype has a round rather than a rectangular or square flow channel to improve flow dynamics and prevent blockage,” Riedel said.
A further prospective multicenter study will evaluate safety and effectiveness of the device in refractory glaucoma in 70 eyes of 70 patients from 12 study sites.
Improving accessibility to glaucoma care
If long-term data confirm the good results achieved so far, the BAM could become the least invasive option in the MIGS panorama.
“It could be used in all forms of glaucoma and across the glaucoma spectrum from mild to severe. Also, unlike other devices, it is conceived as a stand-alone procedure rather than an adjunct to cataract surgery,” Riedel said.
The ease of implantation and the intrinsic infection barrier properties of the device make it suitable for implantation in a minor operating room as opposed to a surgical suite.
“For this and other reasons, it could be an ideal solution for glaucoma in developing regions. It is quick and easy to implant, and you can treat a lot of patients with a simple procedure. It could greatly improve accessibility to glaucoma care worldwide,” Riedel said. – by Michela Cimberle
- For more information:
- Patrick J. Riedel, MD, can be reached at Minnesota Eye Consultants, 11091 Ulysses St. NE, Blaine, MN 55434; email: email@example.com.
Disclosure: Riedel reports he is a consultant for MicroOptx.