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K. Nakauchi, T. Fujikado, J. Ohta, T. Tokuda, H. Kanda, Y. Terasawa, M. Ozawa, A. Hirakata, Y. Tano; Safety and Effectiveness of Suprachoroidal–Transretinal Stimulation by Chronically Implanted Electrode With Continuous Electrical Stimulation in Rabbits . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1530.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have reported suprachoroidal–transretinal stimulation (STS) effectively elicited EEPs using chronically implanted electrode over 3 weeks in rabbits (ARVO 2004). In this report, we investigated the safety and effectiveness of STS method by continuous electrical stimulation with a durable current intensity for platinum electrode (<font face="symbol">f</font>=200µm, I=100 µA). Methods: A newly developed single platinum bump–shaped active electrode (<font face="symbol">f</font> = 200µm), which was embedded in polyimide stripes (2x4mm) and coated with parylene, was implanted into the scleral pocket. The urethane–coated platinum wire (<font face="symbol">f</font> = 100µm), exposed at the tip was implanted into the vitreous as a return electrode. The screw–type recording electrodes were fixed on the skull. One was over the visual cortex and the other was over the bregma. For electrical stimulation, biphasic pulse trains (intensity: 100µA, duration: 0.5ms, frequency: 20 Hz) were used. Biphasic pulse trains were injected for an hour everyday for 2 weeks. The voltage between the active and the return electrode was monitored by oscilloscope to measure the impedance. Before and one–hour after stimulation, EEP with monophasic pulse stimulation (intensity: 300µA, duration: 0.5ms) was recorded to evaluate the retinal function. After the chronic electrical stimulation for two weeks, fundus examination and fluorescein angiography were performed to evaluate the retinal damage. The rabbit eye was then enucleated for histological study. Results: The average of EEP amplitude elicited by 300uA monophasic pulse before stimulation was 14.8 ± 3.8 µV, and after stimulation was 12.0 ± 3.5 µV (n=3). The voltage between active and reference electrode was stable among each rabbit. Funduscopy and fluorescein angiography showed no apparent change in the retina and the choroid. Although histological study revealed no evidence of retinal damage, there was a mild inflammatory change in the sclera around the electrode. Conclusions: Chronic electrical stimulation with a durable current intensity for platinum electrode did not cause significant change to the retina functionally and anatomically. The stability of the impedance indicated that the attachment between electrode and sclera was maintained well.
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