A Three-Dimensional Multi-Resolution Impedance Method for Low-Frequency Bioelectromagnetic Interaction

Abstract

A three-dimensional multi-resolution admittance method has been developed, tested, and shown to be capable of reducing computational cell counts by over 50% while maintaining a high level of accuracy. The method was used to investigate the properties of retinal prosthesis electrode configurations situated in anatomically realistic models of the ocular orbit. These simulations indicated that the epi-retinal electrode array which places the electrodes against the retinal surface is a viable candidate for precise ganglion cell stimulation. The trans-retinal electrode array, in which the electrodes were placed outside of the eye, against the sclera, was shown to not be a suitable solution.

Two-dimensional simulations were used to determine current spread characteristics of coaxial electrodes in a high-resolution retinal model. As total electrode width was increased, a gradual transition from a quadratic to linear relationship between current density induced in the ganglion cell layer and electrode size was observed. Furthermore, two-dimensional simulations were used to estimate the infuence of imperfect retina electrode contact for epi-retinal electrodes by placing a conductive channel between the two surfaces. The general shape of the current patterns was found to be similar, but the current densities were reduced between 0-27% in the model with the conductive gap.