New technologies promise sharper artificial vision for blind people.

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A grid of photodiodes, implanted in the eye of a person with macular degeneration, is one of several devices under development to restore vision.Pixium Vision SA/Paris
▼ CHICAGO, ILLINOIS—In 2014, U.S. regulators approved a futuristic treatment for blindness. 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. Its job: Replace signals from light-sensing cells lost in the genetic condition retinitis pigmentosa. The implant’s maker, Second Sight, estimates that about 350 people in the world now use it. Argus II offers a relatively crude form of artificial vision; users see diffuse spots of light called phosphenes. “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. “It’s a very low bar.”
But it was a start.
He and others are now aiming to raise the bar with more precise ways of stimulating cells in the eye or brain. At the annual meeting of the Society for Neuroscience here last week, scientists shared progress from several such efforts. Some have already advanced to human trials—“a real, final test,” Palanker says. “It’s exciting times.”
Several common disorders steal vision by destroying photoreceptors, the first cells in a relay of information from the eye to the brain. 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.
Because 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. But this spatial mapping gets more complex along the relay, so some researchers aim to activate cells as close to the start as possible.
Palanker’s team has designed a retinal implant of about 400 photodiodes or “pixels” that replace some of the retina’s spatial map. 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. The Paris-based company Pixium Vision is testing the device in five people who have the photoreceptor-destroying disease macular degeneration. 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 artificial vision is good enough to make out the title of a book, Palanker says, though not the words on its pages. His team is now working to shrink the photodiodes—creating finer pixels and sharper vision—without losing too much signal strength.
To push to higher precision than electrical stimulation of the eye can achieve, (▪ ▪ ▪)

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Thanks a ton for sharing such advancements in the fields of optometry...