Cortical activation via an implanted wireless retinal prosthesis.

PURPOSE To demonstrate local cortical activations in the primary visual cortex of the cat as a result of retinal electrical stimulation by means of a completely wireless-controlled, implantable retinal prosthesis in a series of acute experiments. METHODS The transfer of energy to drive the device and signals to activate any combination of 25 retinal electrodes was achieved completely wirelessly by an external transmitter positioned in front of the eye. Individually configured electrical stimuli were applied via any combination of 25 electrodes, on sending the necessary pulse parameters to the implant. Placement of the implant onto the retinal surface was achieved after lensectomy and vitrectomy in the cat. Fixation was performed with a retinal tack. Cortical activation patterns were recorded by means of optical imaging of intrinsic signals. RESULTS Implantation and fixation were successfully performed in three cats. Wireless activation of the implant by radiofrequency was demonstrated by recording of stimulus artifacts from the sclera. Local activation of the visual cortex measured by optical imaging of intrinsic signals revealed a shift of cortical response that was well correlated with a change in the position of the activated retinal electrodes. CONCLUSIONS The results demonstrate the retinotopic activation of the visual cortex using a completely wireless, remote-controlled retinal implant.