Eyes provide early view of Alzheimer’s risk

Protein deposits in the retina and brain appear to parallel possible neurodegeneration, an insight that might lead to easier, quicker detection.

Amyloid plaques are protein deposits that collect between brain cells, hindering function and eventually leading to the death of neurons, fundamental units of the the nervous system that ensure vital information and instructions are relayed throughout the body.

Considered a hallmark of Alzheimer’s disease, amyloid are the focus of multiple investigations designed to detect them, reduce them, remove them or prevent their formation, including the US-wide A4 study. However, amyloid deposits may also occur in the retina of the eye, often in patients clinically diagnosed with Alzheimer’s, suggesting similar pathologies in both brain and eye.

Longevity.Technology: World Alzheimer’s Day is observed on 21st September every year to raise awareness and promote education of Alzheimer’s. Research from San Diego does just that, suggesting that just like the proverbial windows to the soul, the eyes can be a gateway to what’s going on in the brain. Non-invasive retinal imaging may be useful as a biomarker for detecting early-stage Alzheimer’s and risk of Alzheimer’s – early detection is vital, and the earlier the better. Scanning the eye is not only non-invasive, but could be done at local clinics, even at high street opticians. We recently covered Occuity whose hand-held, non-contact optical glucose meter will allow people to check their glucose levels in a non-invasive way. Within their product pipeline, the Occuity team plan to look at using their technology to develop an Alzheimer’s screening device – watch this space!

In a small, cross-sectional study, a team of researchers, led by scientists at the University of California San Diego School of Medicine, compared tests of retinal and brain amyloids in patients from the A4 study and another study (Longitudinal Evaluation of Amyloid Risk and Neurodegeneration) assessing neurodegeneration risk in persons with low levels of amyloid.

The research team used positron emission tomography (PET) to count the number of curcumin-positive fluorescent retinal spots and, therefore, to determine the amount of retinal amyloid deposition. The retina is a thin layer of at the back of the eye that contains millions of light-sensitive cells; because the retina and the brain both originate from the same embryonic precursors [1], the retina can develop similar pathologic features to those seen in the brain of a person suffering from a neurodegenerative disease.

The findings were published in Alzheimer’s & Dementia, and detailed how the researchers observed that the presence of retinal spots in the eyes correlated with brain scans showing higher levels of cerebral amyloid [2].

“This was a small initial dataset from the screening visit. It involved eight patients,” said senior author Robert Rissman, PhD, professor of neurosciences at UC San Diego School of Medicine and director of the Biomarker Core for the Alzheimer’s Disease Cooperative Study and the Shiley-Marcos Alzheimer’s Disease Research Center at UC San Diego. “But these findings are encouraging because they suggest it may be possible to determine the onset, spread and morphology of AD – a preclinical diagnosis – using retinal imaging, rather than more difficult and costly brain scans.

“We look forward to seeing the results of additional timepoint retinal scans and the impact of solanezumab (a monoclonal antibody) on retinal imaging. Unfortunately, we will need to wait to see and analyze these data when the A4 trial is completed [3].”

The next step, said Rissman, will be to conduct a larger study to more fully document and ascertain the relationship between retinal amyloid and cerebral amyloid, both cross-sectionally and over time.

[1] https://www.nature.com/articles/nrneurol.2012.227
[2] https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/dad2.12199
[3] https://ucsdnews.ucsd.edu/pressrelease/eyes-provide-peek-at-alzheimers-disease-risk

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