A novel, ultrathin, multichannel shunt achieved a 40% reduction in mean intraocular pressure (IOP) from baseline with significant medication reduction at 6 months, according to data presented at the American Glaucoma Society’s annual meeting this week in Washington, DC. Eydie Miller-Ellis, MD, a professor of clinical ophthalmology and director of the glaucoma service at the Scheie Eye Institute of the University of Pennsylvania, presented interim results of the VITA trial during Thursday morning’s session.

VITA is a 12-month prospective study, conducted at 3 sites in South Africa, of 15 patients (10 White, 4 Black/African descent, 1 unspecified race) who received the VisiPlate ultrathin subconjunctival aqueous shunt (Avisi Technologies). The subjects (mean age 55.6±17.1 years) had open-angle glaucoma and no prior filtration surgeries. Mean baseline IOP was 24.1±1.6 mmHg, ranging from 18.8 mmHg to 40.2 mmHg, on multiple medications Dr. Miller said.

Promising Interim Results

“At 6-months follow-up, the mean IOP was 14.0±0.7 mmHg, so we’re thrilled to see that there was a mean percent change from baseline of 40%,” observed Dr. Miller. “Seventy-eight percent of the subjects had more than a 20% IOP reduction on the same number or fewer medications. Medication use decreased from 2.0±1.5 medications at baseline to 0.8±1.1 medications at 6 months.” These results exceeded the primary efficacy endpoints for the study.

One patient implanted with the shunt early in the trial was a 60-year-old woman of Black/African descent; Dr. Miller noted that this subject was the first to complete the 12-month follow-up. “Her baseline diurnal IOP (DIOP) was 18.8 mmHg, but she was unable to remain compliant with her medications,” said Dr. Miller. “At month 12 her DIOP was 9.2 mmHg without any medications and there was no need for needling or other postoperative management. Her visual acuity remained stable at about 20/25 and there was no progression of her cataract. It’s always great to see positive results.”

The VisiPlate had a favorable safety profile, said Dr. Miller, with no reports of serious adverse events (AEs). “Specifically, there were no choroidal effusions that required drainage, there was no loss of light perception, there was no significant edema, and there was no persistent hypotony,” said Dr. Miller. “There was no migration, obstruction, or erosion of the implant itself. The most reported AE was self-resolving pain and a case of hypotony that self-resolved but did not require any intervention. None of our patients required the device to be removed, and none of them needed another glaucoma procedure.”

Building a Better Bleb

The VisiPlate is made from an alumina plate coated with parylene-C, a polymer that has been used in other medical implants. It is 5 mm wide and 9 mm long, with 1 mm of the device in the anterior chamber and the rest residing in the subconjunctival space. At just 5 µm thick, it has a very low profile, which creates a bleb that is more aesthetically pleasing and potentially reduces biomechanical stress and risk of conjunctival erosion, said Dr. Miller. “The thing that differentiates this implant from others is that it has a flat profile with multiple channels,” she explained. “There are a whole series of hexagons that are impressed into the alumina, and in between each hexagon is a channel. The aqueous outflow goes through these multiple channels to the subconjunctival space to form a shallow, diffuse bleb.

“I call it ‘building a better bleb,’ because after trabeculectomy or other filtering surgeries blebs can be very elevated and cause the patient some discomfort,” she continued. “That tendency of bleb shape is partially attributable to the single lumen outflow of other available stents. If all the aqueous is coming out in 1 outflow path, then the aqueous force is more concentrated centrally in the bleb, causing more elevation in that area. Our goal is to have a more diffuse outflow of aqueous that’s more comfortable for the patient.

The VisiPlate shunt is implanted in the subconjunctival space via an ab externo procedure with mitomycin C. Dr. Miller said that the procedure for placement is no more challenging than a standard trabeculectomy. “The surgeons that we worked with in South Africa who had long experience doing trabeculectomies found it easier and faster to do than a standard trab,” she noted.

Dr. Miller believes that this nanotechnology-enabled aqueous shunt has the potential to be a critical tool in glaucoma treatment. “We’re very excited about this. Avisi has submitted an application to the US Food and Drug Administration (FDA) and we’re going through the process now to initiate an FDA-approved trial in the United States,” she concluded. GP