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Takao Endo, Takashi Fujikado, Motohiro Kamei, Hirokazu Sakaguchi, Hiroyuki Kanda, Takeshi Morimoto, Haruhiko Kishima, Kunihiko Konoma, Motoki Ozawa, Kohji Nishida; Identification Of Electrodes In Visual Prosthesis Using Suprachoroidal- Transretinal Stimulation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):443.
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Recently, various types of visual prosthesis have been developed. The position of electrode array can be easily identified in cases with epi- or sub- retinal prosthesis because electrodes are visible under the funduscope. However, in our originally developed visual prosthesis using suprachoroidal- transretinal stimulation (STS), it is difficult to identify the electrode array because it is buried in the sclera. In this study, we tried to identify electrode array with OCT images and investigated the relationship between the position of electrode and that of phosphene which was elicited by electrical stimulation.
The patient was a 67 year-old woman with advanced retinitis pigmentosa and had a vision of light perception (OU). We created a scleral pocket around the insertion of the inferior oblique muscle toward the optic nerve in her left eye (from infero-temporal side) and inserted a 7×7 electrode array in the pocket. The internal device was fixed under the skin of the left temporal area. One week after the surgery, we recorded the position of phosphene in response to the electrode stimulation and examined the position of the electrode array with OCT (SpectralisTM).
When we stimulated the tip electrode of the electrodes array, phosphene was recorded at (only) 2° nasal and 2° upper side from the center of visual field. In OCT slices at or lower area of the fovea, the elevation of choroid, which was presumed position of the electrode array, was observed at temporal side.
The OCT images suggested that the head of the electrode array was positioned just lower temporal side of the fovea. This agrees with the position of scleral pocket created during surgery and with the position of phosphene recorded after surgery. These results suggest that we can insert electrode array by STS method near the fovea as epi- or sub-retinal prosthesis.
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