Simulation of Electrode-Tissue Interface with Biphasic Pulse Train for Epiretinal Prosthesis

Retinitis Pigmentosa (RP) and Agerelated Macular Degeneration (AMD) are diseases causing blindness in a large number of people. In this type of degenerative disease, mostly the photoreceptors are damaged, and thus attempts have been made to electrically stimulate the surviving inner retinal neurons and retinal ganglion cells (RGC) in order to restore vision. In this paper, the electrode-tissue interface is modeled to study the effect of electrode size and distance between the electrode and retina by applying biphasic pulse trains similar to in-vitro experiments and in-vivo trials. Simulations were carried out using the AC/DC module of COMSOL v4.3a with planer electrodes placed over the constitutive layers of retina. Biphasic pulses with varying pulse width, inter pulse interval and amplitude were applied to the stimulating electrode. The model is solved for time and frequency domain. Electric potential in the RGC layer was found to vary both as a function of electrode diameter and distance of the electrode.