![]() Second Sight aims to treat these patients with Orion, an implant of 60 electrodes that sits directly on the visual cortex and feeds the brain signals from a glasses-mounted video camera. Whether the trial participants will gain useful vision should become clear next year, says José-Alain Sahel, an ophthalmologist and neuroscientist testing the technology at the University of Pittsburgh School of Medicine in Pennsylvania and the Vision Institute in Paris.īut therapies targeting retinal cells won't help people who have lost much of their eye to injury or have severe damage to the optic nerve from conditions such as glaucoma. Retinal ganglion cells that take up the gene can then respond to red light projected into the eye. In a clinical trial by Paris-based GenSight Biologics, researchers have injected a harmless virus carrying the gene for a light-sensitive protein into the eyes of five people with retinitis pigmentosa. To push to higher precision than electrical stimulation of the eye can achieve, other teams are turning to optogenetics, a technique for activating cells with light. His team is now working to shrink the photodiodes-creating finer pixels and sharper vision-without losing too much signal strength. The artificial vision is good enough to make out the title of a book, Palanker says, though not the words on its pages. At last week's meeting, Palanker presented videos showing that participants who had been implanted with the prosthesis for about 1 year could recognize objects on a table and read printed or on-screen letters. The Paris-based company Pixium Vision is testing the device in five people who have the photoreceptor-destroying disease macular degeneration. A video stream of the outside world is shown on the inside of a pair of glasses in near-infrared light, which the implant's pixels convert into electrical signals to stimulate the retina's bipolar cells. Palanker's team has designed a retinal implant of about 400 photodiodes or "pixels" that replace some of the retina's spatial map. But this spatial mapping gets more complex along the relay, so some researchers aim to activate cells as close to the start as possible. The other players in the relay often remain intact: the so-called bipolar cells, which receive photoreceptors' signals the retinal ganglion cells, which form the optic nerve and carry those signals to the brain and the multilayered visual cortex at the back of the brain, which organizes the information into meaningful sight.īecause adjacent points in space project onto adjacent points on the retina, and eventually activate neighboring points in an early processing area of the visual cortex, a visual scene can be mapped onto a spatial pattern of signals. Several common disorders steal vision by destroying photoreceptors, the first cells in a relay of information from the eye to the brain. Some have already advanced to human trials-"a real, final test," Palanker says. At the annual meeting of the Society for Neuroscience here last week, scientists shared progress from several such efforts. He and others are now aiming to raise the bar with more precise ways of stimulating cells in the eye or brain. "None of the patients gave up their white cane or guide dog," says Daniel Palanker, a physicist who works on visual prostheses at Stanford University in Palo Alto, California. Argus II offers a relatively crude form of artificial vision users see diffuse spots of light called phosphenes. The implant's maker, Second Sight, estimates that about 350 people in the world now use it. Its job: Replace signals from light-sensing cells lost in the genetic condition retinitis pigmentosa. ![]() The device, called Argus II, sends signals from a glasses-mounted camera to a roughly 3-by-5-millimeter grid of electrodes at the back of eye. regulators approved a futuristic treatment for blindness.
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