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Xiaohong Sui, Yan Yan, Jingjing Sun, Liming Li, Qiushi Ren, Xinyu Chai, ; Suprachoroidal Electrical Stimulation by an MEMS-based Flexible Microelectrode array. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1066.
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© ARVO (1962-2015); The Authors (2016-present)
To explore the spatial characteristics of indirect stimulation of the retina by MEMS based flexible microelectrode arrays and to evaluate the spatial characteristics of suprachoroidal stimulation for visual prosthesis.
Based on MEMS techniques, a 16 microelectrode array in 4 × 4 arrangement was fabricated using single metal layer, and a wide-view electrode array with 60 stimulating sites was also fabricated with dual metal layers. Arrays were implanted into the suprachoroidal space of rabbits for in-vivo test. For the 4 × 4 electrode array, diagonal “L” shapes stimulation and two square shapes- small square using the central four electrodes and large square using the peripheral 12 electrodes-stimulation were applied. Row stimulations were applied with the 60 one. The electrical evoked responses (EEPs) from the primary visual cortex were recorded by a silver-ball electrode array. The amplitudes, maximum locations and spatial spreads of the cortical activities were analyzed.
Cortical responses could be consistently evoked by suprachoroidal stimulation using both types of MEMS microelectrode array. In two diagonal “L” shapes stimulations, maximum cortical responses locations and spatial spreads were similar. While in square stimulations, maximum EEPs locations were at the same place but the responses amplitudes increased and the spatial spread expanded in the large square shape stimulation. Rows stimulation in 60 electrode array showed that horizontally orientated cortical responses could be evoked, which were consisted visuotopically with the row-electrodes horizontal position on the retina. The amplitudes of EEPs increased with increasing stimulus intensity, but the maximum EEPs positions remained unchanged. Differentiated maximum EEPs positions showed up in different row stimulations. The spatial spreads varied with a relatively large responded cortical area resulted in stimulation by rows located under the visual streak.
Preliminary pattern differentiated cortical responses could be evoked by simultaneously stimulation of multiple selected electrodes using the suprachoroidal MEMS based array. Results indicated that this approach may be feasible to potentially restore functional vision for the blinds.
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