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RE Eckmiller, R Hornig, V Ortmann, H Gerding; Test Technology for Acute Clinical Trials of Retina Implants . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2848.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To develop and apply equipment and clinical trial procedures in acute human studies for electrical microstimulation with epiretinally implanted microcontact foils and elicitation of corresponding visual responses. Methods: Slim microcontact foil bands of 1 mm width with a number of stimulation electrodes in a variety of diameters positioned at various distances at the foil head, and a microconnector at the foil tail were used for the acute epiretinal stimulation tests. A multi-channel stimulator chip was used to provide bi-phasic current pulses to any of the microcontacts. A tunable retina encoder was available to mimic intraretinal information processing by mapping optical patterns onto pulse sequences as inputs for the stimulator. In conjunction with clinically indicated vitreoretinal surgery, a soft microcontact foil was epiretinally implanted for a period of less than 30 minutes (Gerding et al., ARVO 2002). Electrode impedances were measured inside the surgery room immediately before the epiretinal implantation of the foil head and after re-explantation. Visual sensation reports during the epiretinal positioning of the microcontact foil were recorded as hand signals or speech. Results: Due to the specific elasticity of the foil, which had been successfully tested in cadaver eyes for the risk of retinal injuries, the foil head could be moved safely within the vitreal cavity to touch the retina and to subsequently conform to the epiretinal surface. Visual sensations were successfully elicited by epiretinal stimulation with selected sequences of constant current pulse amplitudes up to 100µA. Measurement of similar impedances before and after the acute implantation demonstrated the stability of the stimulation electrodes. Conclusion: Both our stimulation technology and implantation technology appear to be safe and appropriate in acute clinical trials for the evaluation of essential retina implant parameters as well as of patient suitability for the corresponding type of learning visual prosthesis.
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