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L.S. D. Colodetti, S.C. Z. Colodetti, A. Ray, M. Seiler, B. Thomas, J. Wang, D. Hinton, G. Qiu, J. Weiland, M.S. Humayun; Mechanical vs. Electrical Damage From Epiretinal Stimulating Electrode in Rat . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1516.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare damage created by mechanical pressure vs. electrical stimulation for a stimulating electrode positioned on the epiretinal surface in rat. Methods: The experiments conformed to the ARVO guidelines for the use of animals in research. Electrodes were inserted in the eyes of 6 pigmented rats (Long Evans): 3 acted as mechanical controls (electrode touching the retina for 1 hour without electrical charge) and 3 were stimulated (electrode touching the retina for 1 hour with electrical charge). One incision was made in the sclera close to the limbus with a 27G needle. The surgeon inserted the electrode into the vitreous cavity. The electrode tip was positioned epiretinally and a specific holder was used to keep the electrode in position while the electrical stimulus was applied. The anesthetized rats were stimulated using an external source with 1mc/cm2 of electrical charge for 1 hour. The follow up period was 2 weeks. Results: In all cases the surgical procedure was without complication. Only 1 rat developed a cataract. Fluorescein angiography showed the average extension of the area of hyperfluorescence in the stimulated rats was twice that seen in the non–stimulated. The results of flash ERG, scotopic phase (rod and maximum response), were normal in control and stimulated cases compared to normal eyes. Histology of the mechanical pressure cases showed integrity of ganglion cells, disorganization of the inner and outer nuclear layer, photoreceptor aggregation (Rosettes), and sub–RPE blood vessels. Histology of the electrically stimulated cases showed mostly preserved ganglion cells, gliosis, disorganization of the inner and outer nuclear layer, photoreceptor aggregation (Rosettes), and RPE damage. Conclusions: Lesions created by electrical stimulation at 1 mC/cm2 in rat retina were larger than lesions created by mechanical pressure without electrical stimulation.
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