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E. Zrenner, D. Besch, K.U. Bartz–Schmidt, F. Gekeler, V.P. Gabel, C. Kuttenkeuler, H. Sachs, H. Sailer, B. Wilhelm, R. Wilke; Subretinal Chronic Multi–Electrode Arrays Implanted in Blind Patients . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1538.
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Assessment of function of subretinal implants, consisting of a chip (3x3x0.1mm, 1500 microphotodiodes, amplifiers and electrodes of 50x50 micrometer, spaced 70 micrometer) and a 4x4 array of identical electrodes, spaced 280 micrometers, for direct stimulation (DS), chronically implanted next to the foveal rim of 2 blind RP– patients.
Chip and DS array are positioned on a small subretinal polyimid foil powered via a subretinal transchoroidal, retroauricular transdermal line ending in a radio–controlled, battery–driven receiver–box (for surgical details see Sachs et al. 2006).
The implants were well tolerated without adverse events. OCTs showed stable attachment of the retina (see Kuttenkeuler et al 2006). According to study plan, the implant was removed in one Patient after 4 weeks. The other patient decided to keep the implant. Here, the results of chronic implantation and subretinal direct stimulation are reported for the first time in patients. The charge injection delivered by 16 DS electrodes was simultaneous or successive in order to present temporal or spatial patterns. Patients reported homogeneously appearing, small, yellowish or greyish phosphenes for individual electrode stimulation. They were able to differentiate spatial patterns, such as lines, angles or a bright square with round corners if all electrodes were switched on. Simultaneous stimulation of four electrodes in a line or a row was reported as "bright yellowish rod with round corners, the size of a match, with four slight indentations on both sides." The patient was able to clearly distinguish horizontal from vertical lines and to correctly describe the alignment and direction of dot movement, if three or four neighbouring electrodes were switched on sequentially at one second intervals. Electrical thresholds assessed by chronaxy measurements of each individual electrode and perceptual correlates remained relatively stable (see Wilke et al 2006)
Chronic subretinal stimulation via small electrodes with a distance of approximately 1° allows the discrimination of patterns consisting of small, bright, steadily appearing dots that can be individually discriminated as well as combined into lines and figures, reliably repeated over weeks via a well–tolerated, still intact subretinal micro–electrode array in blind RP–patients. Supported by BMBF 01KP0008 and Retina Implant AG
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