Programmable Electrical Waveform Generator for the Polyimide Retinal Stimulator

Abstract

Abstract: : Purpose: Feasibility of the retinal stimulation, by strip–shaped polyimide electrode array using programmable electrical waveform generator, was investigated. Methods: Polyimide–based gold electrode array was fabricated based on semiconductor manufacturing. Programmable charge–balanced biphasic waveform generator was designed to modify the amplitude of pulse, the duration of stimulation, stimulation rate and the interval between biphasic pulse. Each electrode in the polyimide electrode array can be turned on and off, and the azimuth of the pulse can be reversed by simple manipulation. Anesthetized rabbits were used in vivo experiments. In the epiretinal group, electrode array was introduced into the vitreous cavity through the sclerotomy site after vitrectomy, and placed onto the retina. In the subretinal group, electrode array was introduced under the subretinal space via transscleral approach without vitrectomy. Stimulating electrode was located near the visual streak of posterior pole and the connection site was kept on the external surface of the sclera. Electrical stimulation of the retina was done with the waveform generator. Results: Waveform generator can provide stable current from 1µA to 5mA with negligible crosstalk between the electrodes. Duration of the pulse and the interval between the pulses can be modified up to 8 ms. The stimulation rate can be increased up to 100Hz. Electrical stimulation of the retina could provoke electrically evoked potential at visual cortex in both subretinal and epiretinal stumulation. Conclusions: The transscleral approach into the subretinal space can be done safely in a rabbit eye. The strip–shaped polyimide microelectrode array may be used in acute and chronic experiments for retinal stimulation.

Keywords: transplantation • retina • vitreoretinal surgery