The aging eye: common degenerative mechanisms between the Alzheimer's brain and retinal disease.

Alzheimer's disease (AD) is a common, incurable, and progressive dementia, characterized by loss of learning and memory and the neuropathologic accumulation of amyloid plaques and neurofibrillary tangles in the brain. A number of similarities between AD pathology and several distinct retinal degenerations have been described, particularly with respect to either glaucoma or age-related macular degeneration (AMD), each a leading cause of vision loss and blindness worldwide. Although comparisons between these diseases may provide important new insights into their pathogenic mechanisms, glaucoma and AMD result in markedly different degenerations. Therefore, analyses of the differences and the similarities between these conditions may prove equally productive. Common mechanisms that appear to underlie all three diseases are explored here, as well as potential use of the retina as a biomarker for AD diagnosis and progression. Based on this comparison, past and current efforts to transfer therapeutic strategies between diseases are discussed.