Simulation of electrode-tissue interface for electrical stimulation of retinal ganglion cells

Retinal prosthesis is designed to electrically stimulate the surviving retinal circuitry when photo-transduction mechanism through the photoreceptors is lost due to certain degenerative diseases such as Retinitis Pigmentosa (RP) and Age related Macular Degeneration (AMD). Understanding the electrode tissue interface becomes important for designing these stimulating microelectrodes for restoring vision. In this paper, a modeling of the electrode tissue interface is presented which explains the effects of the parameters to be considered while stimulating the retinal ganglion cell layer. The simulation was carried out with the AC/DC module of COMSOL Multiphysics software v 4.3a with planer disc electrodes placed over the constitutive layers of retina. Anodic biphasic pulses were applied as the stimulus input. The model is solved in time domain, to study the effect of varying diameter, pulse width, distance from the retina was observed. The proposed model closely resembles the experimental set up and gives insight into the current distribution pattern across the retinal tissue layer.