gms | German Medical Science

Artificial Vision 2013

The International Symposium on Visual Prosthetics

08.11. - 09.11.2013, Aachen

Photovoltaic Retinal Prosthesis: evaluation in-vivo

Meeting Abstract

  • Yossi Mandel - Hansen Experimental Physics Laboratory, Stanford University, Stanford, USA; Department of Ophthalmology, Stanford University, Stanford, USA; Department of Electrical Engineering, Stanford University, Stanford, USA
  • H. Lorach - Hansen Experimental Physics Laboratory, Stanford University, Stanford, USA
  • G. Goetz - Hansen Experimental Physics Laboratory, Stanford University, Stanford, USA; Department of Electrical Engineering, Stanford University, Stanford, USA
  • D. Lavinsky - Department of Ophthalmology, Stanford University, Stanford, USA
  • P. Huie - Hansen Experimental Physics Laboratory, Stanford University, Stanford, USA; Department of Ophthalmology, Stanford University, Stanford, USA
  • K. Mathieson - Institute of Photonics, University of Strathclyde, Glasgow, UK
  • L. Wang - Department of Electrical Engineering, Stanford University, Stanford, USA
  • X. Lei - Department of Electrical Engineering, Stanford University, Stanford, USA
  • T. Kamins - Department of Electrical Engineering, Stanford University, Stanford, USA
  • R. Manivanh - Department of Ophthalmology, Stanford University, Stanford, USA
  • J. Harris - Department of Electrical Engineering, Stanford University, Stanford, USA
  • D. Palanker - Hansen Experimental Physics Laboratory, Stanford University, Stanford, USA; Department of Ophthalmology, Stanford University, Stanford, USA

Artificial Vision 2013. Aachen, 08.-09.11.2013. Düsseldorf: German Medical Science GMS Publishing House; 2014. Doc13artvis17

doi: 10.3205/13artvis17, urn:nbn:de:0183-13artvis172

Published: February 13, 2014

© 2014 Mandel et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Outline

Text

Background: In the photovoltaic approach to retinal prosthesis the camera-captured images are projected onto the retina using pulsed near-infrared (NIR) light. Each pixel in the subretinal implant converts pulsed light into local electric current to stimulate the nearby inner retinal neurons. This study characterized the cortical responses to photovoltaic stimulation and compared them with visual evoked potentials elicited by visible light.

Methods: Subretinal photodiode arrays with pixel sizes of 70 and 140 um were implanted in the subretinal space of rats with normal (WT) and degenerate (RCS) retina. Cortical responses (VEP) to pulsed NIR (915 nm) and visible (635 nm) light stimulation were recorded over a 6 month follow-up period. Stimuli were modulated by pulse duration, peak irradiance and repetition rate.

Results: Stimulation thresholds with 10 ms pulses were 0.5 mW/mm2 for 70um pixels and 0.25 mW/mm2 for 140 um pixels. Latency of the visible light-induced VEP decreased with increasing irradiance, unlike the latency of eVEP, which was significantly shorter, and did not vary with NIR light irradiance. In both, WT and RCS rats the eVEP amplitude increased with peak irradiance and pulse duration, and decreased with increasing frequency in the range of 2–20 Hz, similar to the visible light response. However, from 20 to 40 Hz the VEP continued to decrease, while the eVEP did not change as much.

Conclusions: Robust cortical responses to photovoltaic subretinal stimulation and similarity of the eVEP modulation by NIR irradiance, pulse duration and frequency to VEP modulation by visible light suggest similarity in processing of the retinal responses elicited by both types of stimuli at the visual cortex. The small size and lack of wires makes photovoltaic arrays easy to implant and well tolerated in the subretinal space. Photovoltaic retinal prostheses offer a promising approach to restoration of sight in patients blinded by retinal degenerative diseases.