RALEIGH, N.C. — Six million people in the United States and 25 million worldwide are blind because one layer of cells on their retinas no longer work.



Researchers, including those at North Carolina State University, are working to develop an artificial retina that is already showing progress.



With the help of an experimental artificial retina, a man who has been blind for 50 years is able to recognize high-contrast images.



A tiny camera on a pair of glasses sends signals to a device attached to an implant on the retina.



In people with retinosa pigmentosa or age-related macular degeneration, the photo-receptor cells on the retina do not work.



“We replace this functionality with electrical signals that we provide,” said Dr. Gianluca Lazzi, an associate professor in electrical engineering at N.C. State.



Lazzi is working on just one piece of the artificial retina puzzle. Nine institutions — including five national laboratories — are refining the device to make it smaller, more powerful and less invasive.



The prototype model had just 16 electrodes that stimulate neural cells in the retina.



“We need a large number of electrodes to achieve meaningful vision, like facial recognition. We have demonstrated that we need at least 1,000 electrodes,” Lazzi said.



By the year 2013, researchers believe they will accomplish just that — the ability to recognize a face, or even read. A future version will be wireless, with the camera transmitting to a receiver behind the lens, relaying the signal to the retina.



“It will take years to develop a device that is safe and effective, but we believe that we are paving the road,” Lazzi said.



Only six people have the prototype artificial retina as part of the clinical trial.