Research on neuronal circuitry in degenerated retina allows to understand electric excitability of inner retina neurons by subretinal multielectrode arrays positioned in contact with bipolar cells. Electronic devices consisting of 1500 photodiodes, amplifiers and electrodes, positioned on 3 x 3 mm chips, have been developed, tested and implanted in the subretinal space of 11 blind patients. Proof of concept has been shown that this technique allows blind patients to read letters and to combine them to words, detect and describe unknown objects correctly (banana, fork, knife, cup) approach persons and differentiate at least seven shades of grey. The main questions presently are how to improve this technique for long term application, approach limits of spatial resolution, threshold excitation, damage thresholds, biocompatibility with tissue, biostability of devices, signal processing for improved contrast vision as well as influence of learning and role of saccades. Moreover biochemical hybrids that form chemical synapseshave been lined out and models for mechanisms of electrical excitation of retinal neurons by multielectrode arrays have been developed.
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