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Yukari Nakano, Yasuo Terasawa, Hiroyuki Tashiro, Motoki Ozawa; Assessment of the safety of anodic-first chronic electrical stimulation of the rabbit retina for 1 month using a femtosecond laser-induced porous electrode. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4981. doi: https://doi.org/.
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Anodic-first (AF) current pulses are more effective than cathodic-first (CF) pulses in stimulating the retina from the choroidal side [S. E. John, et al. J. Neural Eng. 2013]. However, to our knowledge the safety of AF stimulation has not been evaluated. In this study, we investigated the safety of AF stimulation on retinal prostheses.
Platinum stimulating electrodes with a femtosecond laser-induced porous surface [Y. Terasawa, et al. Conf. Proc. IEEE Eng. Med. Biol. Soc. 2013] were used to stimulate the retinae of three white rabbits. The electrode array was implanted into the scleral pocket in one eye of each rabbit. Currents were pulsed between the stimulating electrode and return electrode (AF, 1.5 mA, 0.5 ms, 50 Hz, 8 h/day). We performed an ophthalmological examination before implantation and after 1 month of electrical stimulation using fundus photography and optical coherence tomography. Retinal damage was histologically assessed in the tissue samples of the enucleated eyes. The shape of the stimulating electrode before and after implantation was observed with an electron microscope. All procedures were in accordance with the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research. This study was approved by the Institutional Animal Care Committee of Nidek Co., Ltd.
Chronic electrical stimulation for 1 month did not cause any bleeding, opacity, and retinal abnormalities in the retinae of any of the rabbits. However, changes in the shape of the stimulating electrode before and after implantation were observed in one case (Fig. 1).
AF electrical stimulation did not cause damage to the retinae and surrounding tissues and was shown to be safe. However, in one case, a change was observed in the shape of the electrode. This change occurred because the scraping powder owing to the electrode process remained on its surface as well as the cleaning was insufficient.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Fig. 1. Stimulating electrodes before and after implantation
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