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Recipient of the implant shocked his doctors by being able to walk around a room unaided, approach specific people, locate objects on a table, tell time by looking at a clock, and describe seven different shades of gray.

Three blind people in Germany have been fitted with an optical sensor chip implanted behind the retina that has allowed them to see shapes and objects just days after the procedure.

The chip has been developed by a joint effort of the Institute for Ophthalmic Research, Univertsei Tübingen, Germany and Retinal Implant AG, also in Germany, specifically for people who have lost or who are losing their sight by retinitis pigmentosa.

What is retinitis pigmentosa?

Retinitis pigmentosa, also known as RP, is an inherited condition of chronic inflammation in the retina, the light-sensing tissue in the back of the eye. The retina has about 120 million rods that help detect shapes and motion. It has about 6 million cones that detect color. Most of the cones are concentrated in the center of the eye known as the fovea centralis, where they are very densely packed into a region just 0.3 mm (about 1/100 of an inch) across. If anything happens in that area of the eye, color perception may be lost.

There are at least nine different genes that, if any one of them goes wrong, can cause problems with rods in the retina that detect shape and motion. There are over 100 genes that can be mutated and cause loss of function in the color-detecting cones. Because there are so many different genes that can cause the same problem, people with RP can have very different experiences of the disease. Some go blind in childhood. Some retain partial sight all the way through life. Some people develop tunnel vision, and others develop night blindness. At some point in life, however, many people with RP become totally blind.

The nature of the disease, however, is that people have some life experience with sight, so their brains can detect shapes, sounds, and colors if sight is restored. The nerves to the retina continue working even though they don't receive any new visual information. This makes people RP prime candidates for prosthetic vision implants such as the chip recently developed in Germany.

Where will researchers go from here?

The next development in the technique probably will be implanting multiple chips so the user can have a wider field of vision. They will to make sure that images are stable over time and they will continue to develop devices that work inside the body, not outside it, and that will accommodate eye-hand coordination. This technology is not likely ever to accomplish complete restoration of sight, but it will bring some people from a state of total blindness to enough vision to read and accomplish daily tasks by sight.

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  • Zrenner E, Bartz-Schmidt KU, Benav H, Besch D, Bruckmann A, Gabel VP, Gekeler F, Greppmaier U, Harscher A, Kibbel S, Koch J, Kusnyerik A, Peters T, Stingl K, Sachs H, Stett A, Szurman P, Wilhelm B, Wilke R. Subretinal electronic chips allow blind patients to read letters and combine them to words. Proc Biol Sci. 2010 Nov 3. [Epub ahead of print]