Researchers at the University of Southern California's Doheny Eye Institute yesterday announced plans to begin a clinical study of the artificial retina, called the Argus II Retinal Prosthesis System.

The Argus II is the second generation of an electronic retinal implant designed to treat retinitis pigmentosa, a group of inherited eye diseases that affect the retina and can cause blindness, said Mark Humayun, professor of ophthalmology at the Keck School of Medicine at USC. The updated device may eventually be implanted in people suffering from age-related macular degeneration, he said.

The Argus II is designed to take the place of photoreceptor cells in the retina, which capture and process light, according to a statement from the university. The implantable device contains 60 electrodes on an array, which is attached to the retina and used with an external camera and video processing system to provide some sight for patients, the university said.

An earlier generation of the device - which contained 16 electrodes - has been implanted in six patients, Humayun said. These patients can now detect light and motion and distinguish between objects like a cup or a plate, he said.

There are 25 million people in the world who have been blinded or are severely visually impaired from diseases like retinitis pigmentosa or macular degeneration, he said. By 2020 that figure is expected to double.