Retinal Implant Helps the Blind Detect Light

The prototype of an electronic microchip, implanted in the eye under the retina and intended to restore partial vision, has been found successful in patients.

A surgical team headed by Professor Karl Ulrich Bartz-Schmidt and Professor Veit-Peter Gabel inserted a permanent subretinal implant in two patients in October 2005 at the University Eye Hospital in Tübingen (Germany). The patients were then monitored over several weeks. The two patients are able to detect light following stimulation of individual electrodes and can describe patterns generated by complex electrode arrays. The study has proved for the first time that the brain can actually use these signals to generate an image pattern.

Scientists at Retina Implant (Reutlingen, Germany) are primarily developing subretinal implants for patients with retinitis pigmentosa, a hereditary condition that can lead to complete blindness over the course of a patient's life. The prototype implant is comprised of a silicon chip with miniature photosensors, connected to an electronic circuit that controls an array of identical electrodes located at the tip of the implant plate. The electrodes stimulate the nerve cells in the retina, sending impulses via the optic nerve to the brain. Electrical current is supplied via the eye's sclera with the aid of conductors in a thin cable under the skin that lead to a radio-controlled, battery-operated receiver.

For the first time ever worldwide, patients who were previously blind have been able to identify electrical stimulus patterns composed of identical dots. This is fundamental proof that our subretinal implant is the right way to go, said Dr. Walter-G. Wrobel, chairman of Retina Implant's management board.

Eventually, a microchip implant of about 3 mm diameter and about 50 µm thickness, in which 1,500 pixels are arranged, is planned, yielding a visual field of 12° and allowing mobility and object recognition in space to the blind.






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