September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Implications of low prosthetic contrast sensitivity for delivery of visual information
Author Affiliations & Notes
  • Georges A Goetz
    Neurosurgery, Stanford University, Stanford, California, United States
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
  • Richard Smith
    Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, California, United States
  • Xin Lei
    Electrical Engineering, Stanford University, Stanford, California, United States
  • Ludwig Galambos
    Electrical Engineering, Stanford University, Stanford, California, United States
  • Theodore Kamins
    Electrical Engineering, Stanford University, Stanford, California, United States
  • Keith Mathieson
    Institute of Photonics, University of Strathclyde, Glasgow, United Kingdom
  • Alexander Sher
    Santa Cruz Institute for Particle Physics, University of California Santa Cruz, Santa Cruz, California, United States
  • Daniel V Palanker
    Hansen Experimental Physics Laboratory, Stanford University, Stanford, California, United States
    Ophthalmology, Stanford University, Stanford, California, United States
  • Footnotes
    Commercial Relationships   Georges Goetz, None; Richard Smith, None; Xin Lei, None; Ludwig Galambos, None; Theodore Kamins, None; Keith Mathieson, None; Alexander Sher, None; Daniel Palanker, Pixium Vision (P), Pixium Vision (C), Stanford University (P)
  • Footnotes
    Support  NIH grant R01-EY-018608, DOD grant W81XWH-15-1-0009, Stanford Spectrum fund, BWF CASI, Pew Charitable Trusts Scholarship
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 3723. doi:
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    • Get Citation

      Georges A Goetz, Richard Smith, Xin Lei, Ludwig Galambos, Theodore Kamins, Keith Mathieson, Alexander Sher, Daniel V Palanker; Implications of low prosthetic contrast sensitivity for delivery of visual information. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3723.

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

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Abstract

Purpose : To measure contrast sensitivity of the retinal response to subretinal photovoltaic stimulation, and assess its impact on delivery of visual information.

Methods : We measure ex-vivo the full-field contrast sensitivity of healthy rat retina stimulated with white light, and of degenerate rat retina stimulated with a subretinal prosthesis above the flicker fusion frequency (20Hz). We model the effects of fixational eye movements on retinal response by decomposing simulated images on the retina into a static and a dynamic component. We use the measured contrast sensitivity function to predict retinal ganglion cell activity elicited by the dynamic component of the image.

Results : Prosthetic vision exhibits significantly reduced contrast sensitivity and no OFF responses in degenerate retina, with 65% contrast changes required to elicit responses, as compared to 3-7% changes required with visible light. The maximum number of action potentials elicited is, at most, half of its natural counterpart for the ON pathway. Our model predicts that for the majority of natural images the contrast sensitivity of prosthetic vision is insufficient for triggering RGC activity by fixational eye movements. For these images, increasing the contrast alone is insufficient. Therefore, image processing should locally enhance both contrast and sparsity, or stimulation frequencies should be reduced to below the flicker fusion to elicit retinal response.

Conclusions : The low contrast sensitivity and lack of OFF responses hamper delivery of visual information via a subretinal prosthesis. Fixational eye movements, which normally prevent static images from fading, are likely to be insufficient for eliciting responses to natural scenes with subretinal stimulation above flicker fusion frequency. Image pre-processing might alleviate this limitation. Alternatively, subretinal implants may need to rely on lower stimulation frequencies.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

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