Retinal Prostheses in development

Throughout the world, the blind are getting closer to seeing again. The Bionic Eye is in development.

Researchers at the USC Doheny Eye Institute announced today the next step in their efforts to advance technology that hopefully will help patients with retinitis pigmentosa and macular degeneration regain some vision using an implanted artificial retina.

Dr. Mark Humayun uses a small external camera  to transmit images to an implanted 4 mm x 5 mm retina chip with 16 electrodes, which is positioned near the ganglion cell layer of the eye. Six blind patients have been implanted with the device, one has had a device installed for more than three years.

The second generation device, dubbed the Argus II Retinal Prosthesis System, consists of 60 electrodes. The study, which entails tests on 10 volunteers, began in 2007.

In Germany, scientists have been working on developing retina prostheses for more than twenty years. According to the presentations, the electronic retina prostheses convey visual impressions, so-called ‘phosphenes’. Patients participating in a U.S. study were able to distinguish light and dark and to register movement and the presence of larger objects. In addition, early reports from a project being conducted by a German research group led by Profesor Eberhart Zrenner at the University of Tübingen indicated they restored visually impaired patients’ ability to read if the letters were eight centimeters (approx. 3 inches) tall.

There are different systems in competition to be the popular choice. In one of the systems, the sub-retinal implant, the chip is implanted under a layer of nerve cells in the retina. There, like the photoreceptors in the retina, it receives light impulses, converts these into electrical signals and transmits them to the nerve cells of the retina.

In the case of the so-called epiretinal implant the chip is fixed to the upper-most layer of nerve cells. There it receives data from a small camera installed in glasses worn by the patient and likewise converts these into impulses for the nerve cells.


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