Retinal implant
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A retinal implant is a biomedical implant technology currently being developed by a number of private companies and research institutions worldwide. The implant is meant to partially restore useful vision to people who have lost theirs due to degenerative eye conditions such as retinitis pigmentosa or macular degeneration. The technology consists of an array of electrodes implanted on the back of the retina, a digital camera worn on the user's body, and a transmitter/image processor that converts the image to electrical signals and beams them to the electrode array in the eye. The technology, while still rudimentary, would allow the user to see a scoreboard type image made up of bright points of light viewed from about arm's length. While currently development is aimed only at the disabled, this technology, once perfected, will revolutionize the personal computing and cyborg industries.
There are two types of retinal implants currently showing promise in clinical trials: Epiretinal Implants (on the retina) and Subretinal Implants (behind the retina).
Epiretinal Implants sit on top of the retina, directly stimulating ganglia using signals sent from the external camera and power sent from an external transmitter, where Subretinal Implants sit under the retina, stimulating bipolar or ganglion cells from underneath. Some subretinal implants use signals and power from external circuitry, while others use only incident light as a power source and effectively replace damaged photoreceptors leaving all other structures within the eye untouched. However, due to a lack of an external power source, the image signal in this second type of subretinal implant may not be as strong as that given by an externally powered epiretinal or subretinal implant.
