Amyloid plaques, which are protein deposits found between brain cells, can cause neuronal death and hinder function. These plaques are a hallmark of Alzheimer's Disease (AD) and have been the subject of numerous investigations, including the A4 national study.
Amyloid deposits can also be found in the retina, which is often seen in AD patients. This suggests that both organs may have similar pathologies. A small cross-sectional study was conducted by researchers at the University of California San Diego School of Medicine to compare brain and retinal amyloid tests in patients from both the A4 study as well as another study (Longitudinal Evaluation of Amyloid risk and Neurodegeneration), which assessed neurodegeneration risk for persons with low levels of amyloid.
Researchers found that retinal spots in the eyes were correlated with brain scans showing greater levels of cerebral amyloid, much like the "windows of the soul". This suggests that noninvasive retinal imaging could be useful in detecting AD risk early on.
These findings were published in the August 17, 2020 issue of Alzheimer's & Dementia.
"This was an initial dataset from the screening visit. Robert Rissman PhD, senior author and professor of neurosciences at UC San Diego School of Medicine, said that the study involved eight patients. He is also the director of the Biomarker Core at UC San Diego and the Alzheimer's Disease Research Center. These findings are encouraging, as they show that it is possible to diagnose AD's onset, spread, and morphology using retinal imaging rather than expensive and difficult brain scans. We are eager to see the results of additional retinal scans at different time points and the effects of solanezumab (a monoclonal anti-inflammatory drug) on retinal imaging. We will have to wait until the A4 trial is over to view and analyze these data.
Rissman said that the next step will be to carry out a larger study in order to better document and ascertain the relationship between cerebral amyloid (both cross-sectionally) and retinal amyloid (over time).
Co-authors include: Jennifer Ngolab and Shaina Korouri, UC San Diego; Michael Donohue, Alison Belsha, Jennifer Salazar, Paula Cohen, Sandhya Jaiswal, Veasna Tan, Devon Gessert, Paul S. Aisen and Michael S. Rafii, all at University of Southern California; Neelum T. Aggarwal, Rush University Medical Center; Jessica Alber, University of Rhode Island; Ken Johnson, NeuroVision Imaging Inc; Gregory Jicha, University of Kentucky; Christopher van Dyck, Yale University; James Lah, Emory University; Stephen Salloway, Butler Hospital, R.I.; Reisa A. Sperling, Brigham and Women's Hospital/Massachusetts General Hospital, Boston.