Realization of a 15-channel, hermetically-encased wireless subretinal prosthesis for the blind.

A miniaturized, hermetically-encased, wirelessly-operated retinal prosthesis has been developed for implantation and pre-clinical studies in Yucatan mini-pig animal models. The prosthesis conforms to the eye and drives a microfabricated polyimide stimulating electrode array with sputtered iridium oxide electrodes. This array is implanted in the subretinal space using a specially-designed ab externo surgical technique that affixes the bulk of the prosthesis to the surface of the sclera. The implanted device includes a hermetic titanium case containing a 15-channel stimulator chip and discrete power supply components. Feedthroughs from the case connect to secondary power- and data-receiving coils. In addition, long-term in vitro pulse testing was performed on the electrodes to ensure their stability for the long lifetime of the hermetic case. The final assembly was tested in vitro to verify wireless operation of the system in biological saline using a custom RF transmitter circuit and primary coils. Stimulation pulse strength, duration and frequency were programmed wirelessly using a custom graphical user interface. Operation of the retinal implant has been verified in vivo in one pig for more than three months by measuring stimulus artifacts on the eye surface using a contact lens electrode.