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Published in:
2016 | OriginalPaper | Chapter
22. Retinal Prostheses
Author : Vinod Kumar Khanna
Published in: Implantable Medical Electronics
Publisher: Springer International Publishing
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Abstract
Severe visual impairment up to the level of blindness is caused by either age-related macular degeneration or retinitis pigmentosa. These are the two usual diseases that lead to degeneration of the outer part of the retina. But even after cellular degeneration in these diseases, i.e., degradation of light-sensing photoreceptors, the remaining visual system of neural networks in the retina may not be damaged in many patients. For such cases, a subretinal implant containing microphotodiodes is placed beneath the retina. Currents produced in the photodiodes by the incoming light energize microelectrodes which stimulate sensory neurons in the retina. Otherwise, an epiretinal implant placed on the surface of the retina is employed along with a video camera. The camera captures the light signal and translates the data into an electrical signal through a microprocessor. This signal is transduced across the nerve cells, through the optic nerve, and eventually to the brain for the conception of an image.