February 2022
Volume 22, Issue 3
Open Access
Optica Fall Vision Meeting Abstract  |   February 2022
Contributed Session I: What limits the spatial resolution of artificial vision in epiretinal implant patients?
Author Affiliations
  • Ezgi Irmak Yucel
    Department of Psychology, University of Washington, USA
  • Michael Beyeler
    Computer Science, UC Santa Barbara
  • Roksana Sadeghi
    Biomedical Engineering, Johns Hopkins University, USA
  • Ariel Rokem
    Department of Psychology, University of Washington, USA
  • Ione Fine
    Department of Psychology, University of Washington, USA
  • Arathy Kartha
    Lions Vision Research and Rehabilitation Center
  • Gislin Dagnelie
    Lions Vision Research and Rehabilitation Center
Journal of Vision February 2022, Vol.22, 12. doi:https://doi.org/10.1167/jov.22.3.12
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      Ezgi Irmak Yucel, Michael Beyeler, Roksana Sadeghi, Ariel Rokem, Ione Fine, Arathy Kartha, Gislin Dagnelie; Contributed Session I: What limits the spatial resolution of artificial vision in epiretinal implant patients?. Journal of Vision 2022;22(3):12. doi: https://doi.org/10.1167/jov.22.3.12.

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

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Abstract

Introduction: Retinal implants provide artificial vision to blind individuals through electrically stimulating remaining non-photoreceptor retinal cells. For epiretinal implants, placed over the ganglion cell layer, individual electrodes produce elongated ‘streaks’ due to the unselective stimulation of underlying ganglion axons (Beyeler, 2019). Here, to examine whether these axonal streaks explain the poor spatial acuity of prosthetic patients, we measured two-point discrimination performance in three patients implanted with an Argus 2 epiretinal implant (Second Sight Medical Products Inc). Methods: On each trial two electrodes were simultaneously stimulated (0.45 um pulse width, 6-20 Hz pulse train, 250-500ms duration, current amplitude 2x threshold). Participants verbally reported the number of distinct percepts they saw. Results: A regression analysis found that current amplitude, physical distance, distance along the axon, and distance between axons all played a significant role in determining whether participants saw one or two percepts. Conclusions: Participants were less likely to see two distinct percepts when electrodes were physically close or lay close to the same axon bundle. Electrodes with high stimulation thresholds were also less likely to produce distinct percepts. Thus electrode pairs can merge into a single percept when (1) current fields overlap, (2) their current fields stimulate the same axonal bundle, or (3) the elongated percepts overlap.

Footnotes
 Funding: UWIN, NIH
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