Subfoveal scotomas trigger fine-scale fixation reorganization: insights from retinal imaging and retinal-contingent stimulation

Abstract

Fine spatial vision relies on the foveola, the 1-degree retinal region with highest cone density. Despite its importance, the relationship between retinal anatomy, fixational behavior, and visual perception in the foveola is not fully understood. Using an Adaptive Optics Scanning Light Ophthalmoscope for high-resolution retinal imaging and stimulation, we studied the effect of a simulated subfoveolar ({approx}0.03 degrees2) scotoma on fine spatial vision and fixation behavior in healthy observers. Our findings show that the visuomotor system adapts to the scotoma with striking precision by shifting the preferred locus of fixation in a systematic fashion by minute ({approx}5 arcmin) amounts to bring stimuli into a region of visibility. These results reveal an unprecedented level of fine-scale plasticity in the human visuomotor system. Interestingly, this new retinal locus of fixation is characterized by lower cone density among those surrounding the scotoma, indicating that factors beyond spatial sampling maximization influence these fine-scale adjustments.