Electrode design to optimize ganglion cell activation in a retinal neuroprosthesis: A modeling study

Reduction of crosstalk in parallel stimulation of the retina is a major issue in improving the performance of retinal prostheses. A three-dimensional (3D) microelectrode array (MEA) has been proposed to mitigate the effect of the electric crosstalk. The efficacy of this configuration in focal electrical stimulation of retinal ganglion cells (RGCs) was investigated by way of an inhomogeneous but isotropic passive model of the retina. The effect of electrode diameter, height of chamber cavity and distance between electrode and RGCs on restricting the spread of electric fields within the retina was investigated. Finite element simulation demonstrated that in comparison with planar microelectrode arrays, an optimal 3D MEA configuration decreased the electric crosstalk and had the capacity to improve the spatial resolution of perceived images. Increasing chamber cavity height was found to become more effective in achieving simulated activation with closer proximity to the target RGCs.