June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
The role of stimulation selectivity in visual acuity with subretinal prostheses
Author Affiliations & Notes
  • Bing-Yi Wang
    Physics, Stanford University, Stanford, California, United States
  • Mohajeet Balveer Bhuckory
    Opthalmology, Stanford University, Stanford, California, United States
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
  • Zhijie Charles Chen
    EE, Stanford University, Stanford, California, United States
  • Andrew Shin
    Material Science and Engineering, Stanford University, Stanford, California, United States
  • Nathan Jensen
    EE, Stanford University, Stanford, California, United States
  • Ludwig Galambos
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
  • Keith Mathieson
    Institute of Photonics, University of Strathclyde, Glasgow, United Kingdom
  • Theodore Kamins
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
    EE, Stanford University, Stanford, California, United States
  • Paul Werginz
    Technische Universitat Wien, Austria
  • Daniel V Palanker
    Opthalmology, Stanford University, Stanford, California, United States
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
  • Footnotes
    Commercial Relationships   Bing-Yi Wang Pixium Vision, Code P (Patent); Mohajeet Bhuckory None; Zhijie Charles Chen Pixium Vision, Code P (Patent); Andrew Shin None; Nathan Jensen None; Ludwig Galambos None; Keith Mathieson None; Theodore Kamins Pixium Vision, Code C (Consultant/Contractor); Paul Werginz None; Daniel Palanker Pixium Vision, Code C (Consultant/Contractor), Pixium Vision, Code P (Patent)
  • Footnotes
    Support  NIH (Grants R01-EY-027786, and P30-EY-026877), DoD (Grant W81XWH-2210933), AFOSR (Grant FA9550-19-1-0402), Wu Tsai Institute of Neurosciences at Stanford, and unrestricted grant from the Research to Prevent Blindness.
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 4607. doi:
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    • Get Citation

      Bing-Yi Wang, Mohajeet Balveer Bhuckory, Zhijie Charles Chen, Andrew Shin, Nathan Jensen, Ludwig Galambos, Keith Mathieson, Theodore Kamins, Paul Werginz, Daniel V Palanker; The role of stimulation selectivity in visual acuity with subretinal prostheses. Invest. Ophthalmol. Vis. Sci. 2023;64(8):4607.

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

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Abstract

Purpose : Photovoltaic subretinal prosthesis provides form perception in patients blinded by age-related macular degeneration, with a visual acuity closely matching the 100μm pixel size. Prosthetic vision could be achieved through network-mediated stimulation via bipolar cells (BCs) or direct activation of the retinal ganglion cells (RGCs), but little is known about how each mechanism contributes to form perception. Better understanding of the role of selectivity in retinal stimulation is crucial for guiding the future development of higher-resolution prosthetics.

Methods : Subretinal photovoltaic devices were implanted in rats, including bipolar arrays of 100μm pixels (with local return electrodes) and monopolar arrays of 40μm pixels (with a global common return at the edge of the implant). Synaptic blockers were delivered intravitreally to evaluate the direct activation of RGCs. Cortical responses to near-infrared (880nm) stimuli, with and without the synaptic blockers, were measured to assess the full-field stimulation thresholds and the grating acuity. Finite element models in COMSOL and multi-compartmental models in NEURON were built to simulate the BC and RGC responses under pertinent electric fields.

Results : For bipolar arrays, the stimulation threshold with blockers was about 10 times higher than without, indicating a large dynamic range for selective stimulation of BCs. For monopolar arrays, the full-field threshold with blockers was approximately 3 times higher than without. More importantly, cortical response to alternating gratings with stripe width below 200μm was only observed without blockers’ presence, indicating that direct stimulation of RGCs does not provide resolution better than the average size of their receptive field: about 200μm in rats. Computational models showed that the dendritic summation and axonal activation in RGCs contributed to the spatially randomized firing under patterned stimuli, including gratings and Landolt C’s.

Conclusions : Network-mediated retinal response might be essential for form perception under patterned stimulation by subretinal prostheses, while direct activation of RGCs likely elicits light perception (phosphenes), but not formed vision. To ensure high selectivity for BCs in subretinal stimulation, the electric field confinement needs to be thoughtfully engineered through hardwired implant design and/or dynamic control of the stimuli.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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