Depth perception in Alzheimer's disease.

Abnormal depth perception contributes to visuospatial deficits in Alzheimer's disease. Disturbances in stereopsis, motion parallax, and the interpretation of static monocular depth cues may result from neuropathology in the visual cortex. We evaluated 15 patients with mild Alzheimer's disease and 15 controls matched for age, sex, and education on measures of local stereopsis (stereoscopic testing), global stereopsis (random dots), motion parallax (Howard-Dolman apparatus), and monocular depth perception by relative size, interposition, and perspective. Compared to controls, the patients were significantly impaired in over-all depth perception. This impairment was largely due to disturbances in local stereopsis and in the interpretation of depth from perspective, independent of other visuospatial functions. Patients with Alzheimer's disease have disturbed interpretation of monocular as well as binocular depth cues. This information could lead to optic interventions to improve their visual depth perception.