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Cortical Activation Via an Implanted Wireless Retinal Prosthesis

¹From the Department of Ophthalmology and the ⁵Institute of Materials in Electrical Engineering, RWTH Aachen University, Aachen, Germany; the ²Department of Neurophysiology, Ruhr-Universität Bochum, Bochum, Germany; the ³Department of Anatomy, Histology, and Embryology, University of Debrecen, Debrecen, Hungary; the ⁴Fraunhofer Institute for Microsystems and Electronics, Duisburg, Germany; the ⁶Neural Prosthetics Group, Fraunhofer Institute for Biomedical Engineering, St. Ingbert, Germany; and the ⁷Institute of Microsystems, University of Freiburg, Freiburg, Germany.

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.

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