Laird Harrison

August 12, 2014

SAN DIEGO — Retinal implants can provide some vision in patients blinded by retinitis pigmentosa, new studies show.

"The results are very encouraging in some patients," said Stanislao Rizzo, MD, a retina specialist from Pisa, Italy, who presented some of the findings here at the 32nd Annual Meeting of the American Society of Retina Specialists.

Retinal implants are the only treatment that can improve vision in patients with retinitis pigmentosa. The inherited condition leads to photoreceptor degeneration but leaves the inner retinal layers intact. This explains why electrical stimulation of the inner retina causes patients to perceive phosphenes.

The Argus II retinal prosthesis system, developed by Second Sight in California, works by stimulating inner retinal cells. A glasses-mounted camera with a battery-powered video processing unit sends signals to the implant, which consists of a scleral band, internal coil, and retinal surface electrode array.

The implant electrically stimulates the retina, causing signals to be transmitted through the optic nerve to the visual cortex. Patients perceive this stimulation as spots of light.

Only preliminary data on its effectiveness have been presented. Dr. Rizzo provided some of the first longer-term results on 10 patients with the implants.

Preliminary Data

The researchers tested the ability of the patients to locate squares of light on a computer screen and detect the direction of motion on a screen.

Twelve months after implantation, square localization had improved in 9 of the 10 patients, and motion detection had improved in 7. "Of course, we had the best results in patients with better visual acuity in the preoperative period," Dr. Rizzo reported.

In addition, the patients showed improvement in sound localization. Restoring vision may affect hearing and quality of life in these patients "by increasing their capacity for orientation in space," he explained.

The researchers also used functional MRI to measure activity in the occipital areas of the brain when patients were shown flashes of black or white rectangles. The activity increased after the implants were placed.

There were no severe adverse reactions, but an error in surgery caused 1 patient to experience a shallow choroidal detachment.

During the same session, data on the Alpha IMS implant, developed by Retina Implant AG in Germany, were presented by Caroline Chee, MBBS, from the National University of Singapore. Whereas Argus II is an epiretinal implant, Alpha IMS is a subretinal implant.

Twelve months after implantation, enough vision had been restored to be useful in daily life in 46% of the 26 patients she reported on.

"It's fantastic technology," said session moderator David Williams, MD, who is in private practice in Minneapolis and was not involved in either study.

Both studies showed that "this sort of device can offer benefits to select patients with severe retinitis pigmentosa," he told Medscape Medical News.

"They confirmed previous evidence that the procedure can be done with relative safety, that with experience the procedure time decreases significantly, and that patients gain benefit from it. We're in the embryonic stages of this type of technology. It just shows that additional research and ongoing development efforts are worthwhile," he said.

In Europe, both Argus II and Alpha IMS have been approved for use by the Conformité Européenne; in the United States, only Argus II is approved by the US Food and Drug Administration.

Dr. Rizzo has disclosed no relevant financial relationships. Dr. Chee reports financial relationships with Novartis and Bayer. Dr. Williams reports a financial relationship with Genentech.

32nd Annual Meeting of the American Society of Retina Specialists (ASRS). Presented August 10, 2014.


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