Perception of Dynamic Displays by People with Argus® II Retinal Prostheses

Artificial vision can be elicited by stimulating the retina, which elicits flashes of light called phosphenes. For phosphenes to be utilized as part of a visual neuroprosthesis, images from one's visual surroundings must be recorded and translated into neural stimulation paradigms. While visual neuroprostheses have led to improvements in orientation and mobility for people with visual impairments, functionality is still limited. This is largely due to low resolution and a narrow field of view, and because artificial vision with current systems is so fundamentally different from natural vision. In this study, our goal was to evaluate if artificial vision could be delivered in a more strategic way for conveying information to visual prosthesis users. For example, blinking phosphenes could be used to signify imminent obstacles in one's surroundings. Four human participants who had Argus® II epiretinal prostheses performed a growing/shrinking object task and two variations of a blinking task. Just two out of the four participants could identify if a square pattern of phosphenes was growing or shrinking with better than chance accuracy. Only one individual could identify if a square/plus-sign pattern was growing or shrinking, with no participants achieving accuracy greater than 80%. All participants could determine whether a single virtual object was continuously visible or blinking at a rate of 1 Hz when stimulation pulse frequency was set to 6 Hz (accuracy $\geq 90\%$ ). When two virtual objects were shown, one blinking and one constant, at different ends of the visual field, only two participants could correctly report which side of the visual field contained the blinking stimulus. Based on these findings, we conclude that epiretinal neuroprostheses could incorporate single-object blinking as one form of visual feedback.