If you think of medical prostheses, then artificial limbs, hip replacements or cochlear implants may spring to mind. These are all undoubtedly impressive feats of medical engineering, but scientists are now attempting to develop something altogether more complex – a retinal prosthesis. This is a device designed to restore some vision to blind people by bypassing damaged photoreceptors in the retina and stimulating the neuronal cells at the end of a still healthy optic nerve. Some dozen research groups around the world – both academic and commercial – are developing these devices, bringing together ophthalmologists and surgeons with physicists and engineers.
Such is the sophistication of the human visual system that it seems unlikely that artificial retinas will ever be able to restore 20/20 vision to someone who is completely blind. But implants have now been fitted to more than 30 blind people and have enabled some volunteers to see dots and lines, and, it is claimed by some groups, to tell basic objects apart, such as a plate from a cup from a knife. Artificial retinas are likely to become commercially available within the next few years, and by then should have improved to the point where they allow blind people to live more independent lives.
In the March issue of Physics World, Edwin Cartlidge looks at how different research groups have approached the design of retinal prostheses, of which some might have sufficient resolution to let patients read text on a page.
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