Micro-shunt, laser duo a novel glaucoma therapy

August 1, 2005

The shunt is also novel because it allows surgeon control of the amount of fluid that flows from one area to another, a feat made possible in part by the selection of gold for its construction.

Washington, DC-In a pilot study involving three centers, patients with mostly end-stage glaucoma were able to achieve an average IOP reduction of 12 mm Hg after implantation of an ultrathin gold micro-shunt (GMS). Patients were followed for up to 2 years.

The drainage device contains numerous microtubular channels that control the flow of the aqueous humor from the anterior chamber into the natural drainage pathway of the suprachoroidal space. The micro-shunt is one component of the investigational DeepLight Glaucoma Treatment System (SOLX), which also includes a long-wavelength, deep-penetrating titanium sapphire laser.

"When the two devices are used in combination, an additional reduction of 1 to 3 mm Hg can be achieved for each additional microtubular channel on the shunt opened with the laser," said Doug Adams, president and chief executive officer of SOLX, a privately held company that is part of the Photonics Center at Boston University. "We think that we have another 10 mm Hg of potential reduction in IOP available to the doctor and the patient at some other point in time."

Titration to lower levels is accomplished by activating additional channels with the laser.

"In 3, 4, or 5 years from now, rather than adding that second, third, or fourth medication or whatever the number may be, the surgeon can open up another channel and try to get incremental reduction in IOP without adding medication," Adams explained.

Study outcomes Outcomes from the pilot study of the GMS were based only on treatment with the shunt as initially implanted, with 10 channels open.

All 59 eyes had no longer responded to maximal medical therapy and had at least one failed surgical intervention. The mean best-medicated IOP before treatment with the shunt was 28.12 mm Hg. At 24 months, the mean medicated IOP was 18 mm Hg.

Patients, who were treated at sites in Spain and Israel, were typically treated with maintenance therapy of at least one medication following implantation of the micro-shunt.

In a separate study, the laser was used to open additional channels in the shunt in five eyes of patients who had the device implanted 12 months earlier. This action resulted in an average drop of an additional 5 mm Hg of IOP, Adams said.

Investigational devices The DeepLight Glaucoma Treatment System consists of a 790-nm titanium sapphire, flashlamp-excited, solid-state laser and a 24-karat gold biocompatible implant that creates a conduit between the anterior chamber and the suprachoroidal space to reduce IOP.

Both the micro-shunt and the laser are classified as investigational devices and can be used individually or together as a treatment system. The SOLX system has been in development for about 5 years, but no data have been released until recently.

Robert M. Kershner, MD, MS, FACS, presented a paper on a pilot study of the GMS at the American Society of Cataract and Refractive Surgery annual meeting in Washington, DC. Co-author Gabriel Simon, MD, PhD, of Madrid, Spain, director of ophthalmic research at SOLX, and SOLX's Adams later discussed the pilot study and the treatment system in more detail. Dr. Simon leads the SOLX scientific team that includes researchers in Israel, Europe, the United States, and Canada and is a professor of biomedical engineering at Boston University.

"The shunt is a new concept in glaucoma," Dr. Simon explained. "We are using a very small shunt that connects the anterior chamber with the suprachoroidal space, so we are draining aqueous inside the eye. We don't have any bleb on the outside."

Studies have shown a difference of about 5 mm Hg in pressure between the anterior chamber and the suprachoroidal space, and that is the scientific basis behind fluid flow and fluid mechanics in the shunt, Adams said.

However, it is constructed to allow fine-tuning of the channels so that pressure can be lowered incrementally rather than abruptly dropping to zero when the anterior chamber is opened, Dr. Simon said. If pressure dropped too low, the laser could be used at a lower energy level to close some of the channels.