Sound Improves Peripheral Detection: Under a Narrowed Functional Visual Field in Simulated Visual-Field Impairment

Observers search for a target by shifting the “Functional Visual Field” (FVF), a limited window around fixation. FVF is defined as a region that elicits a peripheral target conjecture during a search and a saccade toward that location. Using an eye-tracked head-mounted display, we simulated virtual visual constriction—a primary symptom of glaucoma and retinitis pigmentosa—by applying a gaze-contingent peripheral blur. In sighted individuals, the FVF radius during a visual search is ~ 5–10°. We investigated (1) whether the constriction in the visible field narrowed the FVF, and (2) whether synchronized sound provided under the visual constriction facilitated detection of a peripheral target. In Experiment 1, we estimated the FVF radius from scan paths, target landing rates, and detection rates, and found a monotonic decrease with increasing constriction level. In Experiment 2, a brief binaural pure tone was presented when the distance between fixation and a target fell below the estimated FVF radius, and the search display was simultaneously extinguished. Observers judged whether a target was present in the periphery just before extinction. Sound synchronization increased hit rates without changing false-alarm rates relative to a no-sound condition, indicating that auditory cues selectively improve visual detection near the FVF boundary.