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Yasuo Terasawa, Hiroyuki Tashiro, Yukari Nakano, Motoki Ozawa; Stability of the suprachoroidal electrode array during one-month implantation in rabbit eyes. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4195.
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We have been developing a retinal prosthesis with suprachoroidal transretinal stimulation (STS). The purpose of this study is to quantify the lateral movement of suprachoroidally implanted electrode array after implantation surgery.
Eight 2-channel electrode arrays were suprachoroidally implanted to the eyes of rabbits. After 2-week recovery period, electrical stimulation with 0.75µC/phase at 50Hz was applied to the stimulation electrode for 8 hours per day for 4 weeks. Fundus photography was performed immediately after electrode implantation, after 2-weeks recovery period, after 4-weeks electrical stimulation respectively. The electrode position relative to blood vessels around optic nerve head was estimated from the fundus photos.
Five of eight electrode arrays were visible in fundus photos. Electrode movement at the early phase (movement between the day just after implantation and the day after 2-weeks recovery) was 582±265 µm (Mean vs S.E.M), which was significantly larger than that of the later phase (movement between the day after 2-weeks recovery and the day after 4-weeks stimulation, p<0.05 paired t-test). Electrodes had a tendency to move from temporal to nasal both in the early phase and in the later phase.
The measured movement was less than 1 mm and was comparable to previous similar study (Nayagam et al., PLOS ONE, 2014). The smaller movement in the later phase suggested that the electrode array became stabilized possibly due to the encapsulation of fibrous tissue around the electrode array. The tendency of movement from temporal to nasal suggested that one of the driving forces of electrode movement was the residual stress from the lead which was connected to the electrode and was sutured onto the sclera. Minimizing the stiffness of the lead would help stabilizing the electrode array.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig.1 Estimation of electrode position. A: fundus photo just after electrode implantation. stimulation electrodes are indicated by yellow arrows. B: Blood vessels and electrode positions estimated by the fundus photos.
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