Visual Features of Alzheimer's Disease, Parkinson's Disease, Lewy Body Dementia, and Posterior Cortical Atrophy Syndrome

The majority of people with a progressively dementing illness associated with a neurodegenerative disease (NDD) will have visual processing dysfunction at some point in the course of their disease. This is attributed to the fact that Alzheimer's disease and Lewy body dementias are the most common cause of dementing NDDs and visual processing and visual perceptual impairment is frequent in those diseases. Manifestations include visuospatial, reaching under visual guidance, figure-ground perception, visual motion processing, central color vision processing, visual field loss, shape and letter discrimination, visual recognition, and visual attention. In a small portion of these patients, visual processing and visual perceptual dysfunction is the predominant and the initial clinical features of the illness. Other than visual hallucinations, it is important to recognize that the features of visual dysfunction cannot conclusively help to distinguish between disease entities. Biomarkers will increasingly play a major role in making specific disease-defining diagnoses. Despite the lack of disease-modifying treatments for patients with dementing neurodegenerative diseases, the clinical diagnosis, or biomarker identification, of the underlying disease is important for the care and management of patients.