Evoked Potentials in a Blind Subject with a Microelectronic Retinal Prosthesis

Abstract

Abstract: : Purpose: To report the electrophysiologic findings from a human epiretinal microelectronic prosthesis implanted in one blind subject with Retinitis Pigmentosa. Methods: After informed consent was obtained and the subject met the study qualifications, including having BLP or NLP vision and a non-recordable standard VEP, a Second Sight ® Model 1 prosthesis consisting of 16 electrodes in a 4X4 distribution, was implanted. Using a standard VEP electrode arrangement, with the active electrode in a mid-line position, evoked potentials were recorded on several occasions. Stimulation consisted of both Xenon flash and intra-retinal stimulation using the microelectrode as the external stimulus, via an EER technique. Individual electrodes were stimulated based on pre-determined electrical thresholds. The electrical gradiant was based on clinical units being subtracted from the original threshold levels. Results: VEPs from the Xenon flash remained non-recordable over time and the eye when not stimulated had NLP vision. The evoked potentials generated via stimulation of the microelectrode were both consistently recordable at a single session (M P1 amp = 6.1 uv; S.D. = 0.6 uv) and reliable over time (r = .98; p = .0001). P1 and N2 amplitudes, as well as perception of stimulus brightness, degraded with reduction of electrical stimultion. Conclusions: Evoked potentials can be obtained reliably from a totally blind eye when the implanted microelectrode is stimulated. The evoked potentials correspond to both electrical stimulation and visual perception and provide objective evidence to support the visual perceptions reported by the subject. Evoked potentials from direct electrical and non-electrical stimulation  

Keywords: electrophysiology: non-clinical • retinal degenerations: hereditary • low vision