Pattern recognition with the optic nerve visual prosthesis.

A volunteer with retinitis pigmentosa and no residual vision was chronically implanted with an optic nerve electrode connected to an implanted neurostimulator and antenna. An external controller with telemetry was used for electrical activation of the nerve which resulted in phosphene perception. Open-loop stimulation allowed the collection of phosphene attributes and the ability to elicit perception of simple geometrical patterns. Low perception thresholds allowed for large current intensity range within safety limits. In a closed-loop paradigm, the volunteer was using a head-worn video camera to explore a projection screen. The volunteer underwent performance evaluation during the course of a training program with 45 simple patterns. After learning, the volunteer reached a recognition score of 63% with a processing time of 60 s. Mean performance in orientation discrimination reached 100% with a processing time of 8 s.