July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
Development of an electroencephalogram (EEG) protocol to map electrically-elicited visual responses in blind patients implanted with the Argus II retinal prosthesis
Author Affiliations & Notes
  • Yingchen He
    Department of Psychology, University of Minnesota, Minneapolis, Minnesota, United States
    Department of Ophthalmology, University of Minnesota, Minneapolis, Minnesota, United States
  • Natalie Huang
    Department of Ophthalmology, University of Minnesota, Minneapolis, Minnesota, United States
  • Avi Caspi
    Department of Electrical and Electronic Engineering, Jerusalem College of Technology, Jerusalem, Israel
    Second Sight Medical Products, Inc., Sylmar, California, United States
  • Arup Roy
    Second Sight Medical Products, Inc., Sylmar, California, United States
  • Stephen Engel
    Department of Psychology, University of Minnesota, Minneapolis, Minnesota, United States
  • Gordon E Legge
    Department of Psychology, University of Minnesota, Minneapolis, Minnesota, United States
  • Erik J Van Kuijk
    Department of Ophthalmology, University of Minnesota, Minneapolis, Minnesota, United States
  • Dara D Koozekanani
    Department of Ophthalmology, University of Minnesota, Minneapolis, Minnesota, United States
  • Sandra Rocio Montezuma
    Department of Ophthalmology, University of Minnesota, Minneapolis, Minnesota, United States
  • Footnotes
    Commercial Relationships   Yingchen He, None; Natalie Huang, None; Avi Caspi, Second Sight Medical Products, Inc. (C), Second Sight Medical Products, Inc. (P); Arup Roy, Second Sight Medical Products, Inc. (E), Second Sight Medical Products, Inc. (I), Second Sight Medical Products, Inc. (P); Stephen Engel, None; Gordon Legge, None; Erik Van Kuijk, None; Dara Koozekanani, None; Sandra Montezuma, None
  • Footnotes
    Support  Engdahl Family Research Fund; Minnesota Lions Vision Foundation; Research to Prevent Blindness; Center for Applied and Translational Sensory Science Grant; VitreoRetinal Surgery Foundation Research Grant
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 4572. doi:
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      Yingchen He, Natalie Huang, Avi Caspi, Arup Roy, Stephen Engel, Gordon E Legge, Erik J Van Kuijk, Dara D Koozekanani, Sandra Rocio Montezuma; Development of an electroencephalogram (EEG) protocol to map electrically-elicited visual responses in blind patients implanted with the Argus II retinal prosthesis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4572.

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

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Abstract

Purpose : Long-term visual deprivation often leads to cortical reorganization. It is unclear how electrically-elicited visual perception is represented cortically for blind people who use visual prosthesis devices. This study aims to develop a protocol using electroencephalogram (EEG) to evaluate the retinotopic mapping in users of the Argus II retinal prosthesis (Argus II).

Methods : Patients who were blind due to end-stage retinitis pigmentosa and were implanted with Argus II were invited to participate in this study. In our protocol we bypassed the video signal from the Argus II camera and delivered pre-programmed visual patterns from a computer to the epi-retinal electrodes. Based on fundus photos, we designed patterns to activate three electrodes that were located in the upper retina, corresponding to the lower visual field, or three in the lower retina that corresponds to the upper field. The brain activity was recorded using a 32-channel BioSemi EEG recording system. The duration of each trial was 45 seconds and consisted of 30 stimulation frames. Each stimulation frame lasted 33 ms. Twenty trials were recorded with patterns in the upper and lower retina each. The EEG signal was filtered and detrended to remove background noise and linear drift, synchronized with the onset of the stimulation, and averaged across stimulations. Waveforms elicited by stimulating the upper and lower retina were compared.

Results : Initial results from one subject revealed a visual-field dependent polarity reversal in a component with an onset near 40 ms and peak latency near 55 ms. This component was observed in occipito-parietal sites. The polarity reversal property, latency, and cortical distribution of this component are reminiscent of the C1 component observed in normally-sighted subjects. C1 is the earliest visual-evoked component and is thought to originate from retinotopically mapped visual areas.

Conclusions : Our EEG protocol provides a practical way to evaluate the retinotopic mapping that distinguishes different parts of the visual field in the early visual cortex of retinal implant users. Developing methods to measure the preserved mapping is important for understanding how blind patients utilize the spatial information provided by retinal implant.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

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