December 2002
Volume 43, Issue 13
ARVO Annual Meeting Abstract  |   December 2002
Optical Imaging Reveals 2-Dimensional Patterns of Cortical Activation After Local Retinal Stimulation With Sub- and Epiretinal Visual Prostheses
Author Affiliations & Notes
  • UT Eysel
    Dept Neurophysiology Ruhr-University Bochum Bochum Germany
  • P Walter
    Dept Ophthalmology University Cologne Germany
  • F Gekeler H Schwahn E Zrenner
    Dept Ophthalmology University Tübingen Germany
  • HG Sachs V-P Gabel
    Dept Ophthalmology University Regensburg Germany
  • ZF Kisvárday
    Dept Neurophysiology Ruhr-University Bochum Bochum Germany
  • Footnotes
    Commercial Relationships   U.T. Eysel, None; P. Walter, None; F. Gekeler, H. Schwahn, E. Zrenner, None; H.G. Sachs, V.-P. Gabel, None; Z.F. Kisvárday, None. Grant Identification: BMBF Verbund Retina-Implantat 01KP0007
Investigative Ophthalmology & Visual Science December 2002, Vol.43, 4486. doi:
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      UT Eysel, P Walter, F Gekeler H Schwahn E Zrenner, HG Sachs V-P Gabel, ZF Kisvárday; Optical Imaging Reveals 2-Dimensional Patterns of Cortical Activation After Local Retinal Stimulation With Sub- and Epiretinal Visual Prostheses . Invest. Ophthalmol. Vis. Sci. 2002;43(13):4486.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract: : Purpose: Localized retinal stimulation with miniaturized visual prostheses should be suited to generate spatio-temporal patterns of cortical activation. To conservatively judge the possible resolution, 2-dimensional patterns of cortical activation after focal retinal stimulation with epi- and subretinal implants were obtained by optical imaging of intrinsic signals. Methods: Small microelectrode array chips were acutely implanted sub- or epiretinally into the eyes of adult cats. After surgery single electrodes were electrically stimulated (biphasic, 0.25 ms, 2-100 µA), electric field potentials were recorded in the optic tract to ensure the micro-array function and optical imaging of intrinsic signals in the visual cortex was performed with the Imager 2001 (Optical Imaging, USA). Results: Optic tract field potentials were elicited from all electrodes in the epi- and subretinal electrode arrays with currents between 4 and 78 µA. The 2dimensional patterns of cortical activation revealed a precise cortical retinotopy when repetitively evoked from electrodes spaced by 750µm (epiretinal) or 330µm (subretinal). The peaks of intrinsic activity were well separated and showed a spatial spread of 1.8 mm at half height both for the epi- and the subretinal implants. This is equivalent to a visual resolution of 1.25° at 2° retinal eccentricity. Conclusion: Focal stimulation of the retina with subretinally or epiretinally implanted microelectrode arrays that have been developed in the German retina implant project evokes retinotopically organized activity in the visual cortex. The obtained point spread functions represent the worst possible estimate of spatial resolution, since intrinsic signals visualize supra- and sub-threshold and excitatory as well as inhibitory activity without differentiation. On the basis of this conservative estimate of spatial resolution one can assume that human subjects supplied with this kind of visual prostheses would gain visual information that could considerably improve practical capabilities in everyday life.

Keywords: 554 retina • 621 visual cortex • 431 imaging/image analysis: non-clinical 

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