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D.B. Shire, M. Gingerich, L. Theogarajan, J. Wyatt, J. Loewenstein, S. Montezuma, J. Rizzo; Packaging Development for Retinal Prostheses . Invest. Ophthalmol. Vis. Sci. 2003;44(13):5084.
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Purpose: To determine a biocompatible, hermetic packaging system for the intraocular components of a retinal prosthesis which includes scalable feedthroughs for high-density input/output interconnects. Methods: A comprehensive survey of current and emerging packaging techniques was undertaken in an effort to develop an encapsulation system which is capable of flexing to conform to the contours of the eye, provides protection from body fluids over the patient's lifetime, and is compatible with neighboring tissues. This effort was motivated by the incompatibility of conventional implant packaging using titanium capsules and ceramic feedthroughs with the unique requirements presented by a retinal prosthesis operating with a large number of stimulation sites. Among several approaches investigated, a multi-layered package based on vapor-deposited parylene-C coatings with biocompatible alumina/zirconia ceramic surface treatments was selected and evaluated using extended soak testing in biological saline and animal surgical trials. Results: A Web-based database containing the results of our survey has been developed and will be made available for use by researchers. A statistically designed experiment was utilized to ascertain the optimum parameters for obtaining simultaneous hermeticity and biocompatibility, and our results will be presented at the meeting. It was found that these two potentially opposing objectives were addressed well with a multi-layered encapsulation approach in which the desired functions were implemented a layer at a time. Room temperature CVD-deposited 2 µm thick parylene-C films were found to be effective as a base layer, with biocompatibility enhancements coming from subsequent surface treatments including ion beam-assisted ceramic films. This approach allowed our flexible, microfabricated stimulating electrode array structure to be coated with a pliable film which allowed large numbers of sites to be connected to driving circuitry without the use of discrete signal feedthroughs; hence, the scalability of our design. Conclusion: An extensive survey of available packaging techniques coupled with a statistically designed experimental effort has resulted in the development of an effective packaging approach for retinal prostheses.
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