Biomedical Engineering Reference
In-Depth Information
1
Dynamic Interactions of Retinal
Prosthesis Electrodes with Neural
Tissue and Materials Science
in Electrode Design
Charlene A. Sanders
1
, Evan J. Nagler
1
, David M. Zhou
2
and Elias Greenbaum
1
1
Oak Ridge National Laboratory
2
Second Sight Medical Products, Inc.
Introduction
Visual sensation communicates greater information about the environment than
any other sense. It is a carefully integrated neural interpretation of chemical and
electrical signals that are initiated by photons of light and culminate in cerebral
processes that create and map a complex range of visual percepts. Useful visual
sensation is dependent upon the efficient functioning of all the links in the
visual pathway and the transfer of the signal from image to visual cortex without
interruption. Artificial sight refers to a number of experimental photochemical
and photoelectrical devices that mimic the function of specialized cells in the
optical neuronal network and assume their role if they become impaired by
injury or degenerative disease. One such device, presently under development,
is a microelectrode array retinal prosthesis for the treatment of people who
are blind from retinitis pigmentosa (RP) or age-related macular degeneration
(AMD). In both diseases, the photoreceptor cells (rods and cones) are gradually
destroyed. Patients affected by photoreceptor degeneration slowly lose visual
acuity and eventually become blind. Without viable photoreceptor cells, there are
few options for regaining vision. Defective cells may be replaced by removing
the retina and transplanting a new retina from a compatible donor. Clinical
studies of transplant procedures and immunological studies of transplant survival
and rejection are presently under way [1]. The only other viable option is an
electronic visual prosthesis. The retinal prosthesis (Figure 11.1) is an intraocular
electronic device that can be permanently implanted on the inner retinal surface
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