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D. B. Shire, S. K. Kelly, M. D. Gingerich, O. Mendoza, G. Swider, W. Drohan, J. Chen, J. F. Rizzo, J. L. Wyatt; Operation of a Wirelessly Powered Subretinal Neurostimulator. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3031. doi: https://doi.org/.
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This work is related to the efforts of the Boston Retinal Implant Project to develop a sub-retinal prosthesis to restore vision to the blind.
Custom designed application-specific integrated, programmable stimulator chips having 16 output channels capable of 800 µA bi-phasic current pulses were mounted on flexible circuits together with discrete power supply components and secondary power and data receiving coils. These systems were mated with specially microfabricated, 15 µm-thick, 2.5 mm wide polyimide-based flexible electrode arrays. The arrays were inserted into the subretinal space of Yucatan mini-pigs using an ab externo surgical technique, and the electronic components aside from the electrode array were sutured in the superior nasal quadrant. In the photo, one embodiment of the prosthesis with contact pads for testing purposes is shown; the secondary coils are omitted for clarity.
These wirelessly programmable micro-stimulators were first evaluated in vitro, and the serpentine electrode array design allowed considerable flexibility in the relative placement of the electronics module and the electrode array. The extraocular components conformed to the shape of the eye orbit, and after improvements in the surgical technique and the form of the implanted components, the prostheses were well tolerated, and did not erupt through the conjunctiva. The devices could also be explanted successfully without harm to the animal or to the electrical functioning of the device.
Our team has successfully developed a 16-channel wireless, programmable subretinal micro-stimulator that could be implanted in and explanted from Yucatan mini-pig eyes. Our ongoing goals are to improve the biocompatibility and longevity of the device, and to increase the number of stimulation channels to create a device capable of restoring useful vision for the activities of daily living.
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