Visual system manifestations of Alzheimer's disease

Abstract

Alzheimer's disease (AD) is an increasingly common disease with massive personal and economic costs. While it has long been known that AD impacts the visual system, there has recently been an increased focus on understanding both pathophysiological mechanisms that may be shared between the eye and brain and how related biomarkers could be useful for AD diagnosis. Here, were review pertinent cellular and molecular mechanisms of AD pathophysiology, the presence of AD pathology in the visual system, associated functional changes, and potential development of diagnostic tools based on the visual system. Additionally, we discuss links between AD and visual disorders, including possible pathophysiological mechanisms and their relevance for improving our understanding of AD.

Retinal changes in the Tg-SwDI mouse model of Alzheimer’s disease

“…If AD is detected in its early stages, treatment can commence promptly and therefore be more effective in prolonging the patient’s quality of life by delaying cognitive impairment. The current studies support the idea that characterization of the retinal cholinergic system provides a tremendous opportunity to develop non-invasive biomarkers for dementia and AD (Ikram et al, 2012; Chang et al, 2014; Hill et al, 2014; Kusne et al, 2016; Lim et al, 2016). …”

“…Due to the tremendous necessity to quickly diagnose AD and the high cost of other diagnostic techniques, such as positron emission tomography (Franzco et al, 2017) and magnetic resonance imaging (Kusne et al, 2016), researchers have begun employing numerous visual tests to detect differences in the eyes of individuals suffering from AD, as compared to healthy controls (Berisha et al, 2007; Moschos et al, 2012; Frost et al, 2013; Coppola et al, 2015; Snyder et al, 2016). All these data combined have yielded very important findings.…”

“…object recognition), including deficits in motion perception, contrast sensitivity, stereopsis, temporal resolution, acuity, color, and lower critical flicker fusion threshold (Cronin-Golomb et al, 1995; Rizzo et al, 2000). In 1906, Alois Alzheimer was the first to report the occurrence of visual disturbances in one of his patients Auguste D (Maurer et al, 1997; Kusne et al, 2016). …”

Visual Features in Alzheimer’s Disease: From Basic Mechanisms to Clinical Overview

“…Retinal cells share a common embryonic origin with the brain and indeed are a projection of the CNS [ 49 ]. Further, they have similarities in vasculature, glial cells, neurotransmitter systems, and connectivity with the visual cortex [ 50 ]. Moreover, insoluble aggregation of A β peptides in the eye of double transgenic AD mice has been observed in different retinal layers, mainly the ganglion cell layer (GCL), nerve fiber layer (NFL), photoreceptor layer, and inner plexiform layer (IPL), leading to neuronal damage and visual symptoms [ 51 ].…”

“…A β and NFT aggregation as well as neurodegeneration and axonal damage are found in different brain structures related to visual system functioning [ 50 ]. For instance, in the primary cortex (Brodmann areas 17 and 18) of AD patients, has been described a decrease in neuronal density, and increase in glial density only in area 17.…”