Alzheimer’s Disease in the Retina: Imaging Retinal Aβ Plaques for Early Diagnosis and Therapy Assessment

Background: Definite Alzheimer’s disease (AD) diagnosis at early stages is vital for targeting intervention, yet currently unavailable. Noninvasive detection of the pathological hallmark, amyloid-β protein (Aβ) plaques, is limited in the brain. However, the existence of Aβ plaques in the retina, possibly at presymptomatic stages, may improve early detection of AD. Objective: To summarize clinical and preclinical evidence showing that the retina, an accessible part of the central nervous system, displays abnormalities in AD, especially Aβ plaque pathology. The ability to monitor in vivo retinal plaque dynamics in response to immunotherapy is also assessed. Methods: Literature analysis of retinal AD pathology and imaging is provided. In our studies, systemic curcumin is administered to enable monitoring of retinal Aβ plaques in live APPSWE/PS1ΔE9 transgenic mice by optical imaging. Results: Visual and retinal abnormalities, including early manifestation of retinal Aβ plaque pathology, have been documented in AD patients and animal models. In mouse models, retinal Aβ plaques accumulate with age and decrease in response to immunotherapy, consistent with brain pathology. Here, we demonstrate that retinal plaques can be individually monitored in real time following glatiramer acetate immunization. Conclusion: Translation of noninvasive retinal-plaque imaging to humans could eventually facilitate early and accurate AD diagnosis and therapy assessment.