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J.D. Weiland, D. Guven, G.Y. Fujii, B.V. Mech, R.J. Greenberg, M.S. Humayun; Morphometric Analysis of Chronic Electrically Stimulated Canine Retina . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5272.
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Purpose: To study the effects of chronic electrical stimulation on the retina of normal and retinal degenerate (RCD1) dogs implanted with epiretinal electrode arrays. Methods: A retinal stimulator consisting of an extraocular microelectronic stimulator and an intraocular electrode array was implanted in two blind and three sighted dogs. Three dogs (2 blind, 1 normal) were stimulated for 120 days, and two dogs (both normal) for 60 and 103 days, 8–10 hours/day at levels up to 0.1 mC/cm2. Morphometric evaluation was made of the retina under and adjacent to the electrode array and from the fellow eye. At measurement points every 125 microns, cell counts were obtained of outer nuclear layer (ONL), inner nuclear layer (INL), and ganglion cell layer (GCL) and retinal thickness was measured. Results: Light microscopy showed no obvious changes in the retinal architecture or signs of inflammatory reaction that correlated to electrical stimulation. In all of the blind dogs that were electrically stimulated, the retinal thickness in the stimulated eyes was found to be significantly higher at the area under the electrodes when compared with an adjacent area in the same eye (average retinal thickness in microns, 177 vs. 130 and 61 vs. 53, p<0.05). In one of these blind eyes, cell nuclei numbers in ONL, INL, and GCL were also significantly higher under the electrode area (average cell counts, ONL: 18 vs. 8, INL: 51 vs. 38, GCL: 3.8 vs. 1.2, p<0.05 for all). No trends suggesting decreased cell counts in electrically stimulated retinae were evident. Conclusions: Chronic electrical stimulation of the dog retina at up to 0.1 mC/cm2 for 120 days did not decrease the number of cells in the retina of normal or blind dogs.
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