Optimizing the Electrical Stimulation of Retinal Ganglion Cells

A. E. Hadjinicolaou, C. O. Savage, N. V. Apollo, D. J. Garrett, S. L. Cloherty, M. R. Ibbotson, B. J. O'Brien

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26 Citations (Scopus)

Abstract

Epiretinal prostheses aim to restore visual perception in the blind through electrical stimulation of surviving retinal ganglion cells (RGCs). While the effects of several waveform parameters (e.g., phase duration) on stimulation efficacy have been described, their relative influence remains unclear. Further, morphological differences between RGC classes represent a key source of variability that has not been accounted for in previous studies. Here we investigate the effect of electrical stimulus waveform parameters on activation of an anatomically homogenous RGC population and describe a technique for identifying optimal stimulus parameters to minimize the required stimulus charge. Responses of rat A2-type RGCs to a broad array of biphasic stimulation parameters, delivered via an epiretinal stimulating electrode (200 × 200 μm) were recorded using whole-cell current clamp techniques. The data demonstrate that for rectangular charge-balanced stimuli, phase duration and polarity have the largest effect on threshold current amplitude - cells were most responsive to cathodic-first pulses of short phase duration. Waveform asymmetry and increases in interphase interval further reduced thresholds. Using optimal waveform parameters, we observed a drop in stimulus efficacy with increasing stimulation frequency. This was more pronounced for large cells. Our results demonstrate that careful choice of electrical waveform parameters can significantly improve the efficacy of electrical stimulation and the efficacy of implantable neurostimulators for the retina.

Original languageEnglish
Article number6928461
Pages (from-to)169-178
Number of pages10
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Volume23
Issue number2
DOIs
Publication statusPublished - Mar 2015
Externally publishedYes

Keywords

  • Electrophysiology
  • epiretinal stimulation
  • patch clamp
  • rat
  • retinal prosthesis

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