Analysis of Electrically Evoked Cortical Potentials by Acute Suprachoroidal Electrical Stimulation of Rabbit Retina

Abstract

Purpose: : Acute electrical stimulation was applied on the rabbit retina with suprachoroidally implanted polyimide electrode array, and the electrically evoked cortical potentials (EECPs) were analyzed.

Methods: : The seven-channel polyimide electrode array was fabricated for animal experiment with New Zealand white rabbits. Fourteen eyes were implanted with the stimulation electrode arrays in the suprachoroidal space, and the reference electrode was placed on the scleral surface of the opposite direction from the stimulation electrode or in the vitreous cavity in each eye. Evoked cortical potentials were recorded under repetitive cathodic-first biphasic electrical stimulation of the retina (25-1000µA, 1Hz, 1ms duration, 100 averaging). Recording electrodes were implanted intradurally through stainless steel screws over the visual cortex.

Results: : In all 14 eyes, EECPs could be recorded. The mean threshold of electrical stimulation was 75.4±38.5µA in electric current, which corresponded 28.6±14.6µC/cm² in charge density. The amplitudes of EECPs had linear correlation with the stimulation intensity, while the implicit times were not. The placement of reference electrodes on the sclera or in the vitreous cavity did not affect the results. The mean implicit time of the first negative peak was 18.6±1.5 ms in EECP while it was 21.7±1.2 ms in VEP.

Conclusions: : Electrical retinal stimulation with suprachoroidally implanted polymide electrode array could elicite EECPs in rabbits, which indicates its feasibility in retinal stimulation for artificial retina.

Keywords: retina • electrophysiology: non-clinical