The aim of this proposal is to develop a new generation of miniaturized implantable micro-stimulators suitable for chronic implantation in a patient's eye to treat degenerative diseases of the retina. In this study, we will use polyimide electrode array structures coated with inorganic materials to provide a long-lasting implant-tissue interface. Custom packaging and assembly methods for the prostheses will also be developed. The tasks to be accomplished under this proposal include the microfabrication of multi-layered electrode array structures in polyimide for mating with our micro-neurostimulator designs. We will also evaluate the biocompatibility and biostability of these structures, which will be done in part at the CIVR through both in vitro soak-testing experiments and through survival surgeries in Yucatan mini- pig animal models with active and passive devices. Together with our vendors, we will fabricate new generations of high-density ceramic feedthroughs and incorporate these into state-of-the- art 200-channel hermetic titanium packages for our retinal microstimulators that will lead to clinically relevant visual prosthetics. The relationship between the proposed effort and the ongoing patient care mission of the VA is that these improvements are expected to open up new rehabilitative possibilities through more specific, targeted neural stimulation than has previously been possible- especially for the restoration of truly useful vision to blind patients, but also in other areas of medicine such as deep brain or spinal cord stimulation. In sum, it is our hope that the blind population we serve will ultimately benefit from the improved visual acuity that will arise from our ability to create complex, highly biostable retinal neurostimulators;additionally, the channel capacity and efficacy of future wireless implantable prostheses of all types is expected to be improved.
As the veteran population ages in the years to come, the loss of the ability to perform the activities of daily living resulting from vision loss due, for example, to agerelated macular degeneration (AMD) will occur with great social costs. Action must be taken soon to develop a viable visual prosthesis that can restore truly useful vision to these patients;AMD is the leading cause of blindness in the US. The proposed effort is aimed at technology development that will make this possible. According to the VA's own estimates, the number of veterans with significant visual impairment will reach 430,000 by the year 2011. There exists no current treatment that effectively restores lost vision in the majority of AMD patients, and the urgency of developing rehabilitative means for the growing patient population cannot be overstated.