The Retina: A Different Perspective into Alzheimer’s Disease Screening

Abstract

The field of identifying retinal biomarkers of Alzheimer’s Disease has seen tremendous growth in recent years. The retina has great potential for being used in screening for Alzheimer’s disease (AD); it is the only part of the CNS not shielded by bone, and AD patients have several visual complaints. A number of major biomarkers in the retina have been found, including retinal nerve fiber layer (RNFL) thinning, retinovascular changes, pericyte loss and blood-retinal barrier (BRB) weakening, β-Amyloid (Aβ) deposits, Hyperphosphorylated tau and neurofibrillary tangles (NFTs), and gliosis/inflammation. All of these parallel brain biomarkers. Furthermore, new ocular biomarkers have been found (the efficacy of which is not yet fully proven) - Aβ in the lens, choroid thinning, and visual symptoms. Amyloid biomarkers probably have the most potential among these for screening; however, a multivariable model will be more effective. In the future, the Atlas of Retinal Imaging in Alzheimer’s Study (ARIAS) study, which has already commenced, will search for a wide range of retinal biomarkers in many patients in varying stages of AD and risk levels of AD; it will also explore the interrelationships between those biomarkers to find a potential multivariate screening test for AD. Also, tear fluid could be a potential future biomarker that will be relatively easy to screen. Overall, this field has made great strides in recent years, and has great potential for groundbreaking advances in the near future. The promise of course is to enable simple, inexpensive, widespread and regular screening for AD using retinal biomarkers.