Responses of Rabbit Retinal Ganglion Cells to Subretinal Electrical Stimulation With a Silicon-Based Microphotodiode Array

Abstract

Purpose: : In subretinal prosthesis, retinal ganglion cells (RGCs) are activated through electrical stimulation of the retinal neural network. This study was aimed to evaluate the efficacy of the silicon-based solar cells in evoking responses of RGCs by electrically stimulating the photoreceptor side in the isolated retina.

Methods: : A light-bleached retina of adult New Zealand White rabbit was placed onto the silicon chip of 4x4 microphotodiode array with its photoreceptor side down. The stimulating current was elicited by activating the solar cell with a 532 nm laser light source. The responses of ON or OFF alpha RGCs upon electrical stimulation were recorded extracellularly. The recorded RGCs were then injected with Neurobiotin for cell type identification.

Results: : With the design of the circumvented ground electrode, we have successfully evoked spiking responses of ON and OFF alpha RGCs in the isolated rabbit retina using low power of light to activate the microphotodiode array (equivalent to 0.23 mC/cm²). The charge density dependent response and the frequency dependent pair-pulse suppression were characterized. The spike latency of the RGC responses triggered by electrical stimulation was equivalent to the latency of its light responses, which supports that the activation is mediated by the retinal neural network.

Conclusions: : The reliable activation of RGCs by electrical stimulation in vitro with a microphotodiode array demonstrates the feasibility of the solar cell based subretinal prosthesis, and a potential power free device to restore vision.

Keywords: retina • electrophysiology: non-clinical • ganglion cells