Integrating Eye-Tracking With Cortical Visual Prostheses in Patients Without Eyes: A Case Study

Cortical prostheses aim to provide artificial vision to blind individuals by electrically stimulating the occipital cortex to induce visual sensations called phosphenes. Previous research demonstrates that phosphene location is influenced by gaze position, despite fixed electrode placement in the occipital cortex. However, for patients without eyes, it is unclear whether intended eye movements can still modulate phosphene location and, if they do, whether these movements can be accurately recorded and incorporated into prosthetic control algorithms. As part of a clinical trial using intracortical electrical stimulation via a Utah array implanted into the early occipital cortex as a visual prosthesis interface, we had the opportunity to study a patient who lost both eyes due to traumatic injury. This patient currently wears cosmetic eyes. We initially investigated whether intended eye movements modulated the perceived location of phosphenes, and upon confirming their influence, we explored the possibilities for tracking these movements. We recorded the intended eye movements in four cardinal directions using electrooculogram (EOG) and a video-based eye-tracking system. These recordings were then compared with data obtained from a sighted control participant. Our results demonstrated the feasibility of tracking cosmetic eye movements and revealed a significant correlation between eye position and perceived phosphene locations. Then, we conducted behavioral search experiments in which the patient used intended eye movements to locate target objects present on a screen. The results show that the patient's ability to accurately identify object locations using eye movements as recorded in real time with a video-based tracker on a cosmetic eye. These findings highlight the importance of incorporating gaze position into future visual prostheses, even in patients without eyes.