Complex visual disturbances in Alzheimer's disease.

Although Alzheimer's disease (AD) involves visual association cortex, previous studies have not systematically investigated complex visual disturbances in AD. We examined 30 community-based AD patients, 13 (43%) of whom had complex visual complaints, and compared them with 30 controls on 7 types of complex visual tasks. Despite preserved visual acuity and color recognition, the AD patients were impaired in the visual evaluation of common objects, famous faces, spatial locations, and complex figures. In the AD patients, we found that all 30 had disturbances in figure-ground analysis; 17 (57%) had difficulties visually recognizing actual objects ("agnosia"); those with worse dementia disability had the most complex visual disturbances; and a subgroup (6) with Balint's syndrome performed the most poorly on the complex visual tasks. This study demonstrates that a range of complex visual disturbances are common in AD and suggests that they may result from the known neuropathology in the visual association cortex.