Looking with or without seeing in an individual with age-related macular degeneration impairing central vision.

Abstract

Looking leads gaze to objects; seeing recognizes them. Visual crowding makes seeing difficult or impossible before looking brings objects to the fovea. Looking before seeing can be guided by saliency mechanisms in the primary visual cortex (V1). We have proposed that looking and seeing are mainly supported by peripheral and central vision, respectively. This proposal is tested in an observer with central vision loss due to macular degeneration, using a visual search task that can be accomplished solely through looking, but is actually impeded through seeing. The search target is an uniquely oriented, salient, bar among identically shaped bars. Each bar, including the target, is part of an " $"X$ " shape. The target's $"X$ is identical to, although rotated from, the other $"X$ 's in the image, which normally causes confusion. However, this observer exhibits no such confusion, presumably because she cannot see the $"X$ 's shape, but can look towards the target. This result demonstrates a critical dichotomy between central and peripheral vision.