All six blind patients attained limited sight in an experiment with an “artificial retina,” USC and industry researchers reported at a meeting in Florida last week.

Researchers from the Keck School of Medicine and the Doheny Retina Institute presented data on the first six patients implanted with an intraocular retinal prosthesis—more popularly referred to as an artificial retina—developed and manufactured in partnership with Second Sight Medical Products Inc., of Sylmar, Calif.

According to Mark Humayun, professor of ophthalmology at the Keck School and the lead investigator on the project, all six of the previously blind patients have been able to detect light, identify objects in their environment, and even perceive motion after implantation with the epiretinal device.

These results were presented at ARVO 2005, the annual meeting of the Association for Research in Vision and Ophthalmology, held in Fort Lauderdale, Fla., May 1 – 5.

Data collected as of November 2004 showed that the six patients—who had been implanted with a single prosthesis in their “worse eye” for between five and 33 months—were able to “localize the position of, or count the number of, high contrast objects with 74 to 99 percent accuracy,” Humayun said. In addition, they could discriminate simple shapes—such as figuring out the spatial orientation of a bar or the capital letter L—with 61 to 80 percent accuracy.

The researchers also noted that when there is no electricity running through the device, the subjects do not show any improvement in perceptual acuity, “suggesting that electrical stimulation did not improve the health or function of the retina.”

So far, participants in the study have been people with little or no light perception due to the degenerative eye disease retinitis pigmentosa (RP). Ultimately, however, the device might be used for the millions of people with age-related macular degeneration, or AMD. Humayun noted that there are 25 million people around the globe, including 6 million in the United States, who have been blinded, or are severely visually impaired, due to diseases such as RP and AMD. By 2020, that figure is expected to double, creating a vision-loss epidemic.

Both AMD and RP destroy vision by destroying the retinal cells that allow light to be translated into recognizable images.

Second Sight’s intraocular retinal prosthesis is a first step toward replacing those cells with an implanted four-by-four grid of platinum electrodes embedded in silicone rubber.

The electrodes are wirelessly stimulated through an external controller hooked up to a head-mounted video camera.

The continuing study is being conducted under a Food and Drug Administration Investigational Device Exemption, and is funded by Second Sight Medical Products Inc., Research to Prevent Blindness and the Fletcher Jones Foundation.