3D Electrode Array for Single-cell selectivity in Visual Prosthesis

Abstract

Background : Visual prostheses electrically stimulate nearby neurons to generate artificial vision in patients blinded by retinal degenerative diseases. Current prosthetic devices offer limited spatial resolution that results in unselective stimulation of retinal ganglion cells (RGCs). This can be understood as a falling short of visual prosthesis to generate a complete visual scene with detail perception. In this report, the 3D linear electrode carrier is introduced. Our analysis develops a proof of principle to identify the usefulness of the 3D array to activate selectively single RGCs using small electrode size at the highest-density cell.Methods : A simulation framework was built by locating the 3D linear electrode carrier with the highest-density cell. Stimulation of the 3D carrier is implemented at horizontal meridian in the superior retina within the region of 1 mm away from the fovea centralis. Stimulation in that space is needed for critical functions such as object recognition, reading, and driving. The simulation framework obeyed the RGC density and distribution, ganglionic layer thickness, vertical distribution and cell diameter at the fovea. To verify RGC electrical stimulation, the relevant retinal interface elements and dynamics of the voltage-gated ionic channels were integrated into a 3D computational model in COMSOL Multiphysics.Results : the distribution of stimulus from a single active electrode to ground generates a volume of stimulation equivalent to the volume contained by a single RGC at the highest-density cell. Sensitive retinal tissue is safeguarded from electrochemical reactions caused by excessive charge density, the formation of corrosion and neural tissue heating since the advanced technology of the 3D array injects low thresholds for effective stimulation.Conclusions : The 3D electrode array can provide a safe stimulus to enhance visual resolution that can be delivered by +1000 electrodes. This is required in humans for activities where visual detail is of primary importance and thus relevant for high-resolution vision. The 3D electrode array reveals small proximities of electrodes to cells for activation. This is of an advantage for cells located near and very-deep in the ganglion layer because low thresholds are injected to the electrodes producing a well-defined localization of stimulus, an independent activation that targets single RGCs and a safe stimulus.