Perceptual characteristics of scotomas modulate visual performance under simulated prosthetic vision

Retinal prostheses aim to restore vision in patients blinded by photoreceptor degeneration, yet functional outcomes vary substantially across individuals. Scotomas-regions of reduced or absent visual sensitivity-are a defining feature of retinal degenerative diseases, but their perceptual status is often underappreciated in the design and evaluation of prosthetic vision. Here, we investigated how differences in scotoma perception influence perceptual visual task performance and perceptual representations. Approach. Psychophysical experiments were conducted using a virtual reality (VR) platform that simulated visual field deficits characteristic of retinal degeneration, including age-related macular degeneration (AMD). Two different scotoma conditions, perceptually filled-in (invisible) and solid black, were implemented in a head-mounted display (HMD) environment developed in Unity 3D Game Engine. Participants performed visual tasks while behavioral measures, including accuracy, response time, and eye-tracking metrics, were recorded and analyzed. Main Results. Despite identical visual inputs, task performance showed statistically significant differences depending on the perceptual characteristics (i.e., background-matching vs. black) of the simulated scotoma. Critically, the spatial-frequency performance cost on response time was abolished selectively under the black-scotoma-with-phosphene condition (χ²(3) = 8.72, p = 0.033), whereas it remained significant under all invisible scotoma conditions, indicating that a perceptually distinct scotoma background enhances the detectability of phosphene signals. These differences were reflected corroborated by systematic divergences in gaze trajectory length and terminal fixation location across conditions. Significance. Our findings suggest that variability in scotoma perception constitutes an important, yet underexplored, factor contributing to inter-individual differences in the effectiveness of retinal prosthetic stimulation. Accounting for perceptual properties of scotomas may provide a framework for optimizing stimulation strategies and improving functional outcomes of future retinal prostheses.