Making Artificial Vision Look More Natural

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Newswise In laboratory tests, researchers have used electrical stimulation of retinal cells to produce the same patterns of activity that occur when the retina sees a moving object. Although more work remains, this is a step toward restoring natural, high-fidelity vision to blind people, the researchers say. The work was funded in part by the National Institutes of Health.

Just 20 years ago, bionic vision was more a science fiction clich than a realistic medical goal. But in the past few years, the first artificial vision technology has come on the market in the United States and Western Europe, allowing people whove been blinded by retinitis pigmentosa to regain some of their sight. While remarkable, the technology has its limits. It has enabled people to navigate through a door and even read headline-sized letters, but not to drive, jog down the street, or see a loved ones face.

A team based at Stanford University in California is working to improve the technology by targeting specific cells in the retinathe neural tissue at the back of the eye that converts light into electrical activity.

Weve found that we can reproduce natural patterns of activity in the retina with exquisite precision, said E.J. Chichilnisky, Ph.D., a professor of neurosurgery at Stanfords School of Medicine and Hansen Experimental Physics Laboratory. The study was published in Neuron, and was funded in part by NIHs National Eye Institute (NEI) and National Institute of Biomedical Imaging and Bioengineering (NIBIB).

The retina contains several cell layers. The first layer contains photoreceptor cells, which detect light and convert it into electrical signals. Retinitis pigmentosa and several other blinding diseases are caused by a loss of these cells. The strategy behind many bionic retinas, or retinal prosthetics, is to bypass the need for photoreceptors and stimulate the retinal ganglion cell layer, the last stop in the retina before visual signals are sent to the brain.

Several types of retinal prostheses are under development. The Argus II, which was developed by Second Sight Therapeutics with more than $25 million in support from NEI, is the best known of these devices. In the United States, it was approved for treating retinitis pigmentosa in 2013, and its now available at a limited number of medical centers throughout the country. It consists of a camera, mounted on a pair of goggles, which transmits wireless signals to a grid of electrodes implanted on the retina. The electrodes stimulate retinal ganglion cells and give the person a rough sense of what the camera sees, including changes in light and contrast, edges, and rough shapes.

Its very exciting for someone who may not have seen anything for 20-30 years. Its a big deal. On the other hand, its a long way from natural vision, said Dr. Chichilnisky, who was not involved in development of the Argus II.

Current technology does not have enough specificity or precision to reproduce natural vision, he said. Although much of visual processing occurs within the brain, some processing is accomplished by retinal ganglion cells. There are 1 to 1.5 million retinal ganglion cells inside the retina, in at least 20 varieties. Natural vision including the ability to see details in shape, color, depth and motionrequires activating the right cells at the right time.

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Making Artificial Vision Look More Natural