The Present State of Artificial Retinas

Retinal implants that can provide a crude substitute for vision in some forms of blindness are a work in progress at this time, but the path ahead seems fairly clear:

Some people with artificial retinas can read large letters, see slow-moving cars, or identify tableware. Other patients experience no benefit. The variation can be ascribed in some cases to the exact placement of the neuron-stimulating array in the tissue-paper-thin retina as well as the state of the remaining neurons and pathways in each individual's eye. How well people can learn to use the device and retrain their brain is also important. At its best, the current level of vision is very pixelated. What's seen are bursts of light called phosphenes. "It's not restoring vision like you and I think of, it's restoring mobility. They provide contrast so that someone can see a difference in light and dark to the point where they can tell how to walk through a doorway. This is very much the beginning. Retina prostheses are at the stage cochlear implants were 30 years ago. That technology went from being an aid for lip reading to the point now where children with a cochlear implant can go through normal school and even use mobile phones. With retinal implants, we now know it has clinical benefit to patients, and I think we are going to see this technology develop very rapidly over the next decade."

Thousands of pixels [in comparison to the present 60 or so] will likely be required for facial recognition and other detailed visual tasks, and many artificial retina technologies will have trouble getting to such large numbers of pixels because they depend on wires. Wires are used to connect a power supply to electrodes, which requires a surgical procedure to lay the connection through the eyeball. To avoid this limitation, [researchers] are developing a wireless system that transmits image data captured by a video camera to a photovoltaic chip in the eye. Instead of transmitting visible light to the chip, his system uses near-infrared light that is beamed to flexible arrays of small pixels in the retina. The team has tested the system in blind rats and is now working with a company to test the device in patients. But even thousands of pixels are a long way from one million, "which is roughly what we have in the natural eye. And even at that, there is a lot of processing that the retina does that we are going to be skipping with an artificial retina."



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