Electric Eye: Retina Implant Research Expands in Europe, Seeks FDA Approval in U.S.: Scientific American
Promising treatments for those blinded by an often-hereditary, retina-damaging disease are expanding throughout Europe and making their way across the pond, offering a ray of hope for the hundreds of thousands of people in the U.S. left in the dark by retinitis pigmentosa. The disease—which affects about one in 4,000 people in the U.S. and about 1.5 million people worldwide—kills the retina’s photoreceptors, the rod and cone cells that convert light into electrical signals, which are transmitted via the optic nerve to the brain’s visual cortex for processing.
There is no effective treatment for the condition, but researchers are making great strides to remedy this through implants that stimulate still-active nerves in the retina, the layer of tissue at the back of the inner eye. In mid-November Retina Implant, AG, got approval to extend the yearlong phase II human clinical trial of its retinal implant outside its native Tübingen, Germany, to five new sites—Oxford, London and Budapest, along with two additional locations in Germany.
The company’s implant is a three- by three-millimeter microelectronic chip (0.1-millimeter thick), containing about 1,500 light-sensitive photodiodes, amplifiers and electrodes surgically inserted beneath the fovea (which contains the cone cells) in the retina’s macula region. The fovea enables the clarity of vision that people rely on to read, watch TV and drive. The chip helps generate at least partial vision by stimulating intact nerve cells in the retina. The nervous impulses from these cells are then led via the optic nerve to the visual cortex where they finally lead to impressions of sight.
Thus far, some patients report having a narrow field of vision partially restored, providing them with enough acuity to locate light sources such as windows and lamps as well as detect lighted objects against dark backgrounds. The chip’s power source is positioned under the skin behind the ear and connected via a thin cable.