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T Laube, T Schanze, I Bolle, N Bornfeld; Long Term Follow Up of Epidural Electrodes in Minipigs for Registration of Visually Evoked Cortical Potentials (VEP) and Electrically Evoked Cortical Potentials (EEP) . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4457.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The function of retinal implants needs to be tested in an animal model, which provides a close surgical relationship to human eyes and which allows function tests of the visual prosthesis by the registration of cortical evoked potentials. For this we started implantation and testing of chronically implanted epidural electrodes and visual and electrical retina stimulation in minipigs. Methods: Anesthesia using Propofol, Fentanyl and Midazolam medication was applied to a Göttinger minipig prior to preparation of the skull. Three-channel silver-silverchloride electrodes embedded in plastic were epidurally fixed over the primary visual cortex of one hemisphere. Connection cables were placed subcutaneous. Repeated light stimulation was performed and platinum-polyimide film multielectrode arrays were implanted epiretinally next to the visual streak and fixed with perfluorocarbon liquid via pars plana vitrectomy. Multielectrode arrays were removed from the retina after electrical stimulation. Cortical potentials were recorded after visual and electrical stimulation with short biphasic charge-balanced currents. Animals were allowed to recover after experimental sessions. Results: Over a period of more than eight months the implanted epidural electrodes were successfully used for recording of evoked potentials. Visual stimulation often yielded stronger responses for the contralateral eye. Small changes of response amplitudes in subsequent experiments indicated a stable location of recording electrodes. Postoperative observations showed an attached and unchanged retina. Electrical retina stimulation evoked cortical responses. However, low stimulation threshold requires a close contact of electrodes and retinal surface. Conclusion: The minipig model is appropriate for the implantation of epiretinal stimulation electrodes and for the long term tests of retinal implants by recording of cortical responses with chronically implanted epidural electrodes.
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