Interim FDA study results favorable for gold implants

January 15, 2008

Two models of a 24-karat gold implant are being evaluated in a prospective, randomized study enrolling patients with refractory glaucoma.

Key Points

New Orleans-Implantation of a 24-karat gold microshunt (SOLX, OccuLogix) is showing promise as a safe, effective procedure for lowering IOP in eyes with uncontrolled open-angle glaucoma (OAG), said principal investigator Shlomo Melamed, MD, PhD, at the annual meeting of the American Academy of Ophthalmology (AAO).

The CE-marked gold implant is being evaluated for FDA approval in a multinational, prospective, randomized study. The trial is comparing two models of the device (GMS or XGS-5, and GMS+ or XGS-10), against a glaucoma valve (FP-7 Ahmed, New World Medical). In an AAO free-paper session on glaucoma, Dr. Melamed, director of the Sam Rothberg Glaucoma Center, Goldschleger Eye Institute, Sheba Medical Center, Tel-Hashomer, Israel, reported outcomes from an interim analysis of data collected and outlined the microshunt's positive attributes.

To date, Dr. Melamed has implanted the gold microshunt in more than 100 eyes. He presented analyses based on 32 cases enrolled at his center as part of the FDA study.

"We are encouraged by the IOP-lowering effect achieved in these eyes [in which multiple surgeries have failed]. Now, we are eagerly awaiting the final results of the multicenter study that [we hope] will be available at the end of 2008," he added.

The gold implant measures 5.2 mm long, 2.4-mm wide at the apex, and 3.2 mm wide at the tail. One model (GMS) is 44 µm thick, and the other model (GMS+) is 60 µm thick.

The microshunt, which is implanted in the supraciliary space and extends in to the anterior chamber, is designed to lower IOP by providing a pathway for passive aqueous outflow from the anterior chamber to this space, thereby taking advantage of the natural pressure differential between the suprachoroidal space and the anterior chamber.

Surgical procedure

Dr. Melamed presented a video demonstrating the surgical procedure, which he described as very straightforward with a short learning curve. The procedure involves scleral dissection performed about 2 mm posterior to the limbus to a depth of about 90% total scleral thickness. A pocket is made for the shunt by using the iris plane as a guide to create a scleral tunnel toward the anterior chamber. Entry into the anterior chamber ideally is made directly above the scleral spur. Then, a full-thickness incision is completed into the suprachoroidal space.

After verifying that the wound track is open, the shunt is inserted through the scleral tunnel, its posterior tabs are tucked into the suprachoroidal space, and the device is gingerly advanced back into the suprachoroidal space using a Sinskey hook or 27-gauge needle. The scleral incision is closed with one or two sutures.

"An anterior chamber space maintainer is used in all cases, and the anterior chamber remains deep during the entire procedure," Dr. Melamed said. "The shunt must be handled carefully because it is fragile. There may be a benefit for pushing it as far posteriorly as possible into the suprachoroidal space, because there is evidence that the pressure gradient compared with the anterior chamber is even higher in that region."

FDA study results

The multicenter study is enrolling patients with refractory primary OAG and IOP greater than 21 mm Hg while taking maximally tolerated medical therapy. Patients with IOP of less than 30 mm Hg are randomly assigned to receive the gold implant or the glaucoma valve, and patients with higher IOP are randomly assigned to implantation of the 60-µm thick gold implant or the glaucoma valve.