Alterations of the Visual Perception in Advanced Age-Related Macular Degeneration

Age-related macular degeneration is a retinal disease causing the progressive loss of macular vision, typically in people over 60 years of age. It will become a major public health problem in the next years as the population of aged people is expected to increase. In the advanced stage of the disease, development of the central retinal lesion provokes a central scotoma in the visual field. Consequently, at this stage, patients only rely on the use of peripheral vision to achieve visual tasks. The exclusive use of the peripheral retina itself modifies visual perception by reducing visual acuity and contrast sensitivity, and by increasing crowding effects, i.e. contour interaction. Visual perception is further modified by mechanisms of cortical plasticity taking place following the development of the retinal lesion. These mechanisms induce a variety of perceptual changes including filling-in, altered perception of space and Charles Bonnet syndrome. While some modifications of visual perception, such as reduction of visual acuity and contrast sensitivity are well known, occurrence of other phenomena like crowding effect and Charles Bonnet syndrome is generally underestimated. The aim of this review is to discuss the major factors modifying visual perception in patients with advanced age-related macular degeneration and to relate these phenomena to patients’ visual difficulties in everyday life.