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T. Laube, C. Brockmann, N. Bornfeld, B. Sellhaus, G. Roessler, P. Walter, EPI RET3 Study Group; The EPI RET3 Wireless Intraocular Retina Implant System: Development of Surgical Techniques, Function Tests, and Tissue Compatibility of Electrical Stimulation in Goettinger Minipigs. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5876. doi: https://doi.org/.
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To develop and establish surgical methods for safe implantation and explantation of wireless intraocular retina implant systems. To test the in vivo-function of active retina implants and to evaluate the tissue compatibility of epiretinal electrical stimulation.
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 16 Göttinger minipigs under general anaesthesia. Fourteen of the implants were active, 2 were inactive. After phacoemulsification, complete three port pars plana vitrectomy was performed, and the implant inserted through a scleral incision. The receiver coil was placed behind the iris and the electrode array was fixed onto the central retina with a retinal tack. Electrical epiretinal stimulation was performed in 7 minipigs for 1 hour using short biphasic charge-balanced charges of 0,9 mC/cm2 or 2 mC/cm2, respectively. Animals were observed for a period of 14 days. After sacrificing, the eyes were enucleated and processed for histological evaluation. For explantation the retinal tack was retained and the implant removed through a scleral incision.
The implantation and explantation procedures could be well established and are safely performed with the current design of the retina implant. Intraoperatively a minor reversible punctiform bleeding of the retina occurred in one case and an iris bleeding in a second case. Stimulation artifacts were measured with subconjunctival needle electrodes in 10 of 14 eyes up to a maximum period of 8 months postoperatively, proving successful in vivo-function of the implants. Electrical stimulation of the retina caused no tissue alterations at neither of the charges applied.
The performed surgical procedures are safe and effective. A long-term successful in vivo-function of the retina implants could be documented and charges of up to 2 mC/cm2 are safely applicable to retinal tissue in a time range of 1 hour.
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