Preliminary visual function for the first human with the Intracortical Visual Prosthesis (ICVP)

Abstract

Purpose : The Intracortical Visual Prosthesis (ICVP) is a novel device for creating visual percepts in adventitiously blind individuals. Data on human visual performance using a camera with this device have not been previously reported. We tested the hypothesis that the implantee could discriminate horizontal and vertical orientations of the smallest gratings of the Berkeley Rudimentary Vision Test (BRVT).

Methods : The ICVP consists of multiple wireless floating microelectrode arrays (WFMAs), each with 16 stimulating electrodes. Twenty-five WFMAs were implanted in the right occipital visual cortex of a participant with only bare light perception in an FDA-approved Phase 1 clinical trial (NCT04634383). Groups of electrodes within WFMAs were evaluated across 9 months to measure current thresholds and phosphene positions and persistence. Stimulation for each electrode was provided at 200 Hz, 200 µs cathodic phase duration, and up to 60 µA cathodic current. An off-the-shelf pair of glasses with an integrated camera and USB connection was used to drive stimulation with 6 selected WFMAs, using 4 electrodes per WFMA. During 2 days of exploratory testing, the 50 M BRVT grating was tested at 25 cm in front of the participant (0.15 cycles/degree) in either horizontal or vertical orientation, with 30 balanced, randomized forced-choice trials.

Results : Thresholds under 60 µA were found, individually or in combinations, for 233 electrodes. Thresholds varied across days, but remained stable on average. Of the 6 WFMAs used for camera testing, 4 produced phosphenes within a 4° cluster centered 4° below and left of fixation, and the others located 4° below and 20° left of the central cluster, respectively. Phosphene sizes varied within 0.3–6° across, generally increasing in size with distance from fixation. The participant correctly determined the orientation of the 50 M grating in 27/30 trials (p < 10⁻⁵, binomial test), corresponding to an acuity of 2.3 logMAR or better, responding within 24 s on average (range: 6–91 s).

Conclusions : Using only a small subset of the 233 percept-generating electrodes with the first human-implanted ICVP system and minimal training, the participant, otherwise having only bare light perception, was able to successfully score a grating acuity of 2.3 logMAR or better. Future tests will investigate performance with stimuli at higher acuity levels and more extensive stimulation strategies.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.