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T. Laube, C. Brockmann, C. Krüger, J. Lang, A. Meyer, R. Hornig, N. Bornfeld; Epiretinal Prosthesis With an Episclerally Fixed Receiver Coil for Power Supply: First Results in Göttinger Minipigs . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3189.
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To develop and establish a surgical method for minimal invasive implantation of wireless epiretinal prosthesis. A new implantation technique maintaining the lens is developed in order to reduce surgical traumas.
Wireless epiretinal implants consisting of an HF receiver coil for power supply and an electrode array connected via a flexible cable were implanted into the right eye of 10 Göttinger minipigs under general anaesthesia. A rectangular scleral flap of 8 mm width was prepared with a limbal based hinge. Following pars plana vitrectomy the extraocular receiver coil was sutured onto the scleral surface adjacent to the scleral flap. An incision through the pars plana was prepared under the scleral flap through which the cable bound electrode array of the implant was inserted and fixed epiretinally using a scleral tack. The cable was laid onto the retinal surface. After four (n = 5) or eight (n = 5) weeks the implants were removed and animals were observed for a period of 14 days. After sacrificing, the eyes were enucleated and dissected.
The condition of the sclera at the site of the scleral flap was unirritated and the flap was adherent to the underlying tissues. The flap did not show any filtrations. The extraocular part of the device was completely covered by the conjunctiva. Inflammations were not recognized intraocularly, the electrode array was adjacent to the retina. In few cases the tension of the cable material complicated intraocular handling of the implant, impeding optimal placement onto the retinal surface. A safe and reliable fixation of the electrode array onto the retinal surface has been found to be of major importance.
In comparison to an intraocular fixation of the receiver coil within the capsular bag, the advantages of an implantation technique with extraocular fixation of the receiver coil are the following: shorter period of surgery as lens extraction is not required; incisions are smaller, as the portion with largest diameter – the receiver coil – remains extraocularly, and a hypotonic phase does not occur. Therefore the current development of an epiretinal visual prosthesis focuses on a minimal invasive implantation technique with episcleral fixation of the receiver coil.
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