gms | German Medical Science

Purpose: The Intracortical Visual Prosthesis (ICVP) is a modular implant creating visual percepts in adventitiously blind individuals. Data on human visual performance using a camera with such a device are scarce. We tested our inaugural implantee’s ability to perform meaningful daily living activities.

Methods: The ICVP uses 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 bare light perception in an FDA-approved Phase 1 clinical trial (NCT04634383). Current thresholds and phosphene positions and persistence were estimated, and used to create a map that converts video from a camera to a command stream controlling individual electrodes. Stimuli of up to 200 Hz, 200 µs cathodic phase, and up to 60 µA current were used. Video from off-the-shelf glasses with visible and thermal cameras was used to stimulate 7 selected WFMAs, using 2 electrode groups per WFMA. Functional discrimination tests included 50 M BRVT gratings at 25 cm, common household objects on a table, the direction of a walking person, and occupied vs. empty chairs.

Results: Electrode groups with thresholds <30 µA were used to generate 7–9 phosphenes. Thresholds may vary up to 240% across days (median 16%) but have mostly remained stable over 2.5 years. The participant scored 27/30 correct on 50 M gratings (p<10–5, binomial test). Object discrimination (4-AFC) and size recognition (3-AFC) were 70% correct. Using a visible or thermal camera, the implantee successfully discriminated the direction of a walking person (χ²(2)=22.7) and the position of an unoccupied chair (χ²(2)=35). All test results without stimulation were at chance.

Conclusions: Even with the limited number of distinguishable phosphenes, our initial implantee is highly successful in performing simple daily activities. We expect that improved mapping, now under way, will allow performance of more detailed activities.