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Hiroyuki Tashiro, Yasuo Terasawa, Masayuki Shinomiya, Motoki Ozawa, Toshihiko Noda, Jun Ohta; Long-term Suprachoroidal-transretinal Stimulation By The Bullet-shaped Platinum Electrodes In Normal Rabbits. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4947.
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© ARVO (1962-2015); The Authors (2016-present)
We have been developing retinal prosthesis devices taking approach of Suprachoroidal-Transretinal Stimulation (STS) using bullet-shaped platinum electrodes.The purpose of this study is to evaluate the durability of the bullet-shaped electrodes and the effect of electrical stimulation on living eyeball tissue.
Three eyes of three Japanese white rabbits were used. All procedures conformed to the ARVO Statement for the Use of Animals in Ophthalmic and Vision Research. The implanted electrodes had three bullet-shaped platinum electrodes. The dimensions of electrodes were 500µm in diameter and 500µm in height respectively. Charge delivery capacities(CDCs) of the electrodes had evaluated at more than 0.68µC/Phase (approximately 1.3mA at 500µs duration) for cathodic first(CF) pulses in phosphate-buffered saline(PBS). After a recovery period, chronic stimulation was initiated. The stimulation period was 12 weeks. The applied stimulation currents consisted of CF biphasic pulses with amplitudes of 1mA, durations of 500µs and rates of 50Hz. Electrical stimulation were applied to three eyes for 8 hours per day. Electrode impedances were measured every day. At the end of the stimulation period, funduscopies were obtained, then histological studies of the retinal tissues and observations of the electrodes with a scanning electron microscope (SEM) were performed.
During the stimulation period, the electrode impedances stayed under 2-3kΩ at 1kHz. Histology suggested that no significant tissue damages were induced both the presence of electrodes themselves and the electrical stimulations. After the stimuli, the electrodes did not change in appearance on the SEM.
We succeeded in confirming no injury to the eyeball tissues by the chronic electrical stimulations with the bullet-shaped platinum electrodes. The electrodes showed enough durability and biocompatibility for chronic stimulation in vivo.
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