Gold micro-shunt lowers IOP by 30% in study

The shunt takes advantage of the naturally occurring pressure differential between the anterior chamber and the suprachoroidal space.

Las Vegas-Two-year clinical results show that implantation of a gold micro-shunt in glaucomatous eyes achieved a mean reduction of ≥30% in IOP by 6 months that was maintained at 24 months. Shunt implantation also reduced the number of glaucoma medications required postoperatively, according to Gabriel Simon, MD, PhD. He presented these data in a poster at the annual meeting of the American Academy of Ophthalmology.

The gold micro-shunt (GMS, SOLX) offers a blebless treatment option for patients whose glaucoma is unresponsive to other therapies, said Dr. Simon, director of ophthalmic research at the Boston University Photonics Center, research professor of biomedical engineering at Boston University, and inventor of the GMS.

The effect of implantation is similar to that of cyclodialysis; however, the shunt provides sufficient flow resistance to eliminate the risk of hypotony.

In this nonrandomized study conducted at multiple centers in Israel and Spain, unpaired glaucomatous eyes of 71 patients, ages 45 to 83, had the shunt implanted. Mean baseline IOP was 27.54 mm Hg, and the mean at 24 months was 17.83 mm Hg. At 12 months, 57% of patients had achieved an IOP reduction of ≥30%, he said.

Glaucoma medications were discontinued following surgery but could be resumed at the physician's discretion. In this study, the average number of postoperative medications was 1.2 ± 0.8 versus 2.0 ± 1.2 preoperatively.

Adverse events included one case of shunt extrusion due to improper placement and one case of retinal detachment. Transient hyphema was the most common complication, with 19 cases reported.

All were less than 2 mm, however, and resolved within 1 week postoperatively. Seven cases of transient hypotony also were reported.

The GMS is a tiny, ultra-thin, biocompatible 24-karat gold implant containing microtubular channels that are designed to drain fluid from the anterior chamber of the eye to the suprachoroidal space, reducing IOP.

The shunt takes advantage of the naturally occurring pressure differential between the anterior chamber and the suprachoroidal space, allowing aqueous humor to pass through the microchannels and into the uveoscleral outflow pathways.

Two models available

The company has developed two models of the shunt: the GMS and the GMS+. Both are made of 99.5% medical-grade gold and are 5.2 mm long and 3.22 mm wide. However, the GMS+ is thicker-60 µm versus 40 µm for the original shunt-and the channels are higher-40 µm versus 20 µm.

In studies, the GMS has been shown to provide an average of 6 to 8 mm Hg of IOP reduction, and the GMS+ proves an average reduction of 10 mm Hg.

Both devices have been granted CE approval and are available for sale outside the United States.

A randomized clinical trial comparing the GMS and the GMS+ with the FP-4 Ahmed Glaucoma Valve (New World Medical Inc.) is under way and will include up to 145 eyes at approximately 10 sites in the United States, Canada, and Asia.

"In the next couple of months we will recruit the remainder of the patients that the FDA requires," Dr. Simon said.

In other studies, the investigators will be testing the GMS+2, the latest modification of the shunt design, which offers less restriction of the aqueous flow than the earlier versions of the device.

Investigators are also exploring use of the 790 titanium sapphire laser (SOLX) in conjunction with the micro-shunt, he said.

The laser would be used to photo-titrate the shunt and achieve more targeted reduction of IOP, Dr. Simon concluded.