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H. Ameri, D. Guven, R. Freda, M. Okandan, K. Wessendorf, G. Qiu, J. Weiland, M. Humayun; Surgical Implantation of Epiretinal Prosthesis With Spring–Mounted Electrodes . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1484.
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Purpose: To assess the feasibility of surgical implantation of epiretinal prosthesis with spring–mounted electrodes in dogs and study the histological features after implantation. Methods: The device is a silicon, square 5x5–mm array with 81 electrodes and an attached silicone cable. Electrodes are attached to the array by micro–machined springs and can move perpendicular to the array surface, a maximum of 100µ. Four devices were implanted in dogs: two were implanted acutely during a terminal surgery; two dogs underwent surgery for chronic implantation. All cases underwent standard pars plana vitrectomy with peeling of posterior hyaloid membrane. One of the sclerotomies was extended and the device was introduced into the vitreous cavity and fixed to the retina with a Grieshaber retinal tack. Results: During the acute experiments, some of the electrodes broke and it appeared nearly impossible to introduce the device into the eye without damaging the electrodes. Moreover, insertion in one animal caused some peripheral retinal damage. Observations of the first two acute experiments led to development of a special sleeve–shaped metal tool, for easier insertion of the array into the eye. The insertion tool was used in both dogs that underwent chronic implantation; in both cases all electrodes were intact after implantation. On postoperative day 2, ocular trauma in one dog caused intraocular hemorrhage and dislocation of the implant. In the other dog the eye was enucleated after 2 weeks. Optical Coherence Tomography (OCT) prior to enucleation showed some electrodes were not in close contact with the retina. Histology demonstrated retinal folds and indentation of the retina by some electrodes.Conclusions: This study demonstrated the feasibility of implanting a retinal prosthesis with spring–mounted electrodes, using a special insertion tool. Retinal indentation indicates close contact of some electrodes with the retina. Work is underway to modify the array to ensure all electrodes remain in close contact with the retina.
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