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J. Chen, J. Loewenstein, H.A. Shah, C.D. Herbert, J.F. Rizzo; Extraction of a Chronically Implanted Sub–Retinal Electrode Array . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1488.
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Purpose: To assess the feasibility of extraction of a chronically implanted sub–retinal electrode array. Methods: Inactive, plain, gold wired polyimide strips with and without gold electrodes were surgically implanted into the sub–retinal space of 8 rabbits. Each strip was 10 mm x 1.5 mm x 15 µm. A partial thickness scleral flap (2.5 x 1 mm) was dissected 8 mm posterior to the limbus supero–temporally. After vitrectomy, a Lambert Cannula was used to create a retinal bleb localized over the flap. A guide (2 x 15 mm) was used to help insert the polyimide strip through an incision under the flap into the sub–retinal space. Clinical examination, fundus photographs, and ERG were performed post–surgery and periodically up to 2 months. At 2 months, the polyimide strips were extracted from 6 eyes, followed by periodic examination up to 1 month. Animals were then sacrificed and eyes enucleated for histological examination. As a control, 2 eyes were enucleated without extraction of the strips. Results: Three implantation procedures were performed without significant surgical complications. Five other procedures resulted in a small retinal tear at the edge of the array. Retinal incarceration occurred in 1 procedure, resulting in damage to the retina near the flap. One procedure resulted in a retinal fold near the entry of the strip. The retinal detachments recovered rapidly, and the arrays remained in stable sub–retinal position in all eyes. Four strips have been extracted without difficulty and without complications. The retina was not funduscopically altered in any eye. Conclusions: Using an ab–externo technique, we have successfully implanted and extracted polyimide strips under the retina. Although the retina was damaged minimally in some procedures, this study shows that a prosthesis can be implanted in the sub–retinal space without major complications. Extraction can be performed up to 2 months afterwards without difficulty and without obvious damage.
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