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

Abstract

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.

Correlated Activity in the Degenerate Retina Inhibits Focal Response to Electrical Stimulation

“…Although retinal prostheses have shown some clinical success, a patient’s visual acuity restored with electronic retinal devices is at best less than 20/420 ( Stingl et al, 2013 ; Ayton et al, 2020 ). To improve visual acuity, many engineers have attempted to increase the spatial resolution of electrical devices by integrating a large number of smaller electrodes on an electronic chip ( Zeng et al, 2019 ; Shire et al, 2020 ; Chenais et al, 2021b ), optimizing electrode configurations ( Wilke et al, 2011 ; Celik, 2017 ; Flores et al, 2018 ) or stacking more electrodes in a three-dimensional structure ( Bendali et al, 2015 ; Davidsen et al, 2019 ; Seo et al, 2019 ). Physiologists have searched for optimal stimulation protocols, such as the minimum stimulation threshold required for local activation of target neurons to avoid axon bundle activation or non-specific activation of nearby RGCs ( Sekirnjak et al, 2008 ; Jepson et al, 2013 ; Grosberg et al, 2017 ; Chang et al, 2019 ; Tandon et al, 2021 ).…”