Eyes as a potential window to Alzheimer’s Disease
Friday, December 6th, 2019
Australian scientists have used specialised eye scanning technology to detect changes in the retina that could be indicative of early Alzheimer’s Disease.
Lost Opportunities for Early Intervention
The presence of clumps of beta-amyloid protein in the brain is an established hallmark of Alzheimer’s disease. They can accumulate long before any symptoms of dementia show up.
However, at the moment, the only way to confirm abnormal protein levels is through lumbar punctures or PET scans that require the injection of a radioactive tracer. These tests are invasive and costly, so they are only really reserved for people in clinical trials or with unusual forms of dementia.
Retina Reflections as a Possible Biomarker
The retina is a developmental extension of the brain. Rodent models and post-mortems have shown that beta-amyloid clumps can occur in the retina in Alzheimer’s Disease too. Based on this idea, the Melbourne-based researchers developed a special technology akin to that used in NASA satellites that shines a rainbow coloured light into the eyes. In a trial of the technology, the study team shone the light into the eyes of 15 Australians who showed high levels of beta-amyloid in a PET scan and demonstrated mild cognitive impairment on neuropsychological tests. They compared the way the light was reflected from their retina to how it was reflected in 20 Australians who had no beta-amyloid clumps on a PET scan. The team found that the reflection pattern – what they called the hyperspectral score -was able to discriminate between individuals with higher and lower levels of beta-amyloid in the brain[1].
Healthy Scepticism
The non-invasive imaging takes less than a second to perform. Thus, it has exciting potential to become a cost-effective screener for people at risk of Alzheimer’s Disease. However, some of the research community are still sagely sceptical about the technique. There is disagreement about the extent to which retinal changes parallel brain changes in Alzheimer’s Disease[2]. Could it be that the reflections observed in the study were due to other factors associated with high levels of protein deposits in the brain, for instance? Much more work is needed to determine the exact relationship between hyperspectral scores and protein brain deposits before we can get too excited unfortunately.
[1] https://www.nature.com/articles/s41467-019-12242-1#Bib1
[2] https://onlinelibrary.wiley.com/doi/abs/10.1111/bpa.12070; https://academic.oup.com/jnen/article/76/5/376/3096011
