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R. Wilke, C. Kuttenkeuler, B. Wilhelm, H. Sailer, H. Sachs, V.–P. Gabel, D. Besch, K. Bartz–Schmidt, E. Zrenner, Subretinal Implant Study Group; Subretinal Chronic Multi–Electrode Arrays in Blind Patients: Perception of Dots and Patterns . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3202.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the type of visual perception and the efficacy of pattern recognition elicited by subretinal stimulation with single and multiple electrodes of 50x50 micrometers spaced 280 micrometers.
An array of 4x4 columnar TiN electrodes was implanted into the subretinal space next to the foveal rim of two blind retinitis pigmentosa patients. Single or multiple electrodes were supplied with voltages of different waveforms and amplitudes. Stimulation parameters were optimized to gain prolonged perception of phosphenes. The influence of stimulation parameters on perception with respect to dot shape, size, color, duration and pattern recognition was investigated.
Subretinal stimulation with single electrodes in our patients resulted in an even perception of well demarcated bright yellowish or grayish round dots without glaring. Patients never reported complex or variable shapes when single electrodes were activated. Estimation of dot size and spacing between dots was stable during the whole first study period (4 weeks). Dots related to single electrode stimulation were described as having approximately the size of a pea at arm's length. Changes in stimulation amplitude or frequency led to modulation of perceived brightness and to lesser extent in dot size while shape or color remained unchanged. Activation of multiple electrodes resulted in pattern recognition with single dots often just discernible from each other. Horizontal lines could clearly be discriminated from vertical lines. Subsequent stimulation of electrodes led to recognition of movement and reliable identification of the direction of movement when presented in a four alternative forced choice mode.
It could be demonstrated for the first time that electrical stimulation with subretinal implanted electrodes is capable of eliciting reproducible phosphenes of well defined shape, enabling clear pattern recognition. Stimulation of adjacent electrodes elicited dots of comparable size shape and color.
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