The Effect of Return Electrode Position on Induced Electric Fields for Electrical Stimulation of Retinal Ganglion Cells

Age-related macular degeneration and retinitis pigmentosa are the most countered eye diseases that damage photoreceptors and cause to lose the visual sense. To regain the visual sense, studies are focused on the electrical stimulation of nerve cells remain intact. The electrical stimulation is carried out with the electrode arrays that include a certain number of stimulation electrodes and a common return electrode. In this study, the retinal stimulation is modelled using a computational model to investigate stimulation performance depending on the return electrode position and its geometrical properties. Stimulation induced electric field, current density and temperature over the retinal tissue are examined. It is seen that closer placement of return electrode and stimulation electrodes causes high electric field intensity and current density between electrodes, which is quite risky for long term chronic implementation by the reason of the increase in the temperature beyond the safe limits. It is concluded that there is an indispensability for the distances, three to five times of the electrode diameter, between electrodes to avoid electrode corrosion and tissue damage.