Exploring Alzheimer Disease from a Retinal and Ocular Perspective

Alzheimer disease (AD) is a neurodegenerative disorder currently recognized as the leading cause of dementia worldwide. It is characterized by a progressive cognitive decline, which can be studied and diagnosed through the use of various brain biomarkers. The retina, being part of the central nervous system, shares numerous structural and functional features with the brain. In this light, a wide range of alterations have been found in the retina with significant potential as biomarkers for AD diagnosis, even at early stages of its manifestation in the brain, and for monitoring disease progression within this organ. Furthermore, the detection of such alterations in the eye and retina is feasible through non-invasive, relatively simple and cost-effective techniques, such as optical coherence tomography, scanning laser ophthalmoscopy and electroretinography. Using these methods, numerous studies have identified molecular, morphological and functional changes associated with AD in the retina and other ocular elements, including the choroid, cornea, lens, intraocular humors and tear fluid. This review addresses the main anomalous changes identified to date in the retina and other eye structures in patients with AD, highlighting their potential utility as biomarkers for the diagnosis of this disease and their possible extrapolation to its prognosis in the brain.