July 2019
Volume 60, Issue 9
Free
ARVO Annual Meeting Abstract  |   July 2019
Pillar electrodes reduce in-vivo stimulation thresholds for subretinal prosthesis
Author Affiliations & Notes
  • Elton Ho
    Department of Physics, Stanford University, Stanford, California, United States
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
  • Tiffany Wanshing Huang
    Department of Electrical Engineering, Stanford University, Stanford, California, United States
  • Xin Lei
    Department of Electrical Engineering, Stanford University, Stanford, California, United States
  • Thomas Flores
    Department of Applied Physics, Stanford University, Stanford, California, United States
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
  • Henri Lorach
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
  • Theodore Kamins
    Department of Electrical Engineering, 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
  • Daniel V Palanker
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
    Department of Ophthalmology, Stanford University, Stanford, California, United States
  • Footnotes
    Commercial Relationships   Elton Ho, None; Tiffany Huang, None; Xin Lei, None; Thomas Flores, None; Henri Lorach, None; Theodore Kamins, Pixium Vision (C); Ludwig Galambos, None; Keith Mathieson, None; Daniel Palanker, Pixium Vision (C), Pixium Vision (P)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science July 2019, Vol.60, 4976. doi:https://doi.org/
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    • Get Citation

      Elton Ho, Tiffany Wanshing Huang, Xin Lei, Thomas Flores, Henri Lorach, Theodore Kamins, Ludwig Galambos, Keith Mathieson, Daniel V Palanker; Pillar electrodes reduce in-vivo stimulation thresholds for subretinal prosthesis. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4976. doi: https://doi.org/.

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

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Abstract

Purpose :
Smaller pixels in subretinal prosthesis have higher stimulation thresholds due to limited penetration depth of electric field into the inner nuclear layer (INL). This can be remedied by placing active electrodes on pillar structures, which penetrate into the middle of the INL. Here we evaluate the effects of such implants in-vivo.

Methods :
Photovoltaic arrays with (a) 55 and 40µm pixels having flat geometry (F55 and F40), and (b) pixels with their active electrodes on 10µm tall pillars (Pil55 and Pil40), were implanted subretinally in rats with retinal degeneration (Royal College of Surgeons, RCS). Visually evoked potentials (VEP) were recorded via screw electrodes placed onto the skull above visual cortices on both hemispheres. Collimated NIR laser light (915nm) was projected onto the implant. VEPs were measured using full-field flashes at 2Hz with varying irradiances and pulse durations.

Results : With pillars on 55µm pixels, the irradiance threshold was reduced by nearly a factor of 2 (from 1.0±0.27 to 0.55±0.15 mW/mm2), and the duration threshold decreased by a more than a factor of 3 (from 0.29±0.11 to 0.08±0.02 ms). With 40µm pixels, signals were much weaker, and the effect of the pillars was less pronounced: irradiance threshold decreased by 28% (from 1.8±0.58 to 1.3±0.3 mW/mm2) and duration threshold by 16% (from 0.83±0.17 to 0.7±0.12 ms). VEP waveforms with pillar electrodes were more complex than with flat pixels: they included components with larger latency, each with its own irradiance and duration thresholds.

Conclusions : Lower stimulation thresholds enable wider dynamic range of stimulation, which should provide larger number of resolvable levels of grey - a feature crucial for complex visual tasks, such as face recognition. For image modulation by pulse duration using DMD projector on video goggles, 55mm pixels with pillars may offer 3 times wider dynamic range due to lower duration threshold. However, with 40mm pixels, signals remained quite low despite the pillars, and therefore other geometries should be considered for such small pixels.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

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