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Dorit Raz-Prag, Dov Weinberger, Ra‘anan Gefen; Implantation procedure for retinal prosthesis: adaptation of extracapsular cataract procedure. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1809.
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To develop a surgical technique for epiretinal implantation and attachment of retinal prosthetic device, while considering procedure time, patient comfort and recovery as well as precision of implantation.
Nano Retina dummy implant made of 3D silicon electrodes and glass was used to develop the surgical procedure in the domestic pig. An anterior chamber approach through the limbus and a pars plana approach were tested. Animal well-being, fundus examination and histology were used to evaluate long-term retinal response and effects on the implant.
An incision of approximately 6mm was required to deliver the implant into the eye. In the scleral approach an incision of this size induced bleeding in the pig. The anterior chamber approach was found to be less invasive and therefore preferable to the pars plana approach. The procedure begins in standard anterior capsulotomy, lens aspiration with a phacoemulsifier followed by posterior capsulotomy. Partial pars plana 23G vitrectomy is then performed and the implant is inserted through the anterior chamber via the opening in the posterior lens capsule, followed by in the bag intraocular lens implantation. The remaining vitreous cushions the implant and is gradually removed to allow the implant to advance to the site of implantation. Once at the site, the implant is pressed gently into the retina. The surgery was completed within less than one hour. In chronic follow-ups there were no ill-effects on the animals and the eyes fully recovered. Histopathological evaluation demonstrated that the needle electrodes remained intact and penetrated into the retina. The needle electrodes were sufficient to anchor the implant at the site of implantation.
Implantation surgery through the cornea, an adaptation of the commonly performed cataract surgery followed by lens implantation, was found to be suitable and efficient for epiretinal implantations of this stand-alone epiretinal prosthesis model. Patients who undergo vitreal procedures generally develop a cataract within months and would require lens replacement. This combined procedure circumvents the additional surgery.
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