An eye test could spot Alzheimer's disease two decades before symptoms emerge, a new study claims.
Researchers in Los Angeles trialed the test on 16 patients.
Comparing their results to brain scans, the eye test was just as successful at spotting those with twice the amount of plaque build-up in their brains.
Experts say the finding is one of the biggest breakthroughs in Alzheimer's research to date, offering the first sign of a cost-effective and non-invasive test.
'The findings suggest that the retina may serve as a reliable source for Alzheimer's disease diagnosis,' said the study's senior lead author, Dr Maya Koronyo-Hamaoui, a neurosurgeon at Cedars-Sinai.
Until about a decade ago, the only way to officially diagnose someone with Alzheimer's disease was to analyze their brain posthumously.
In recent years, physicians have been able to use positron emission tomography (PET) scans of the brains of living people, to identify markers of the disease.
However, the technology is expensive, and the test is invasive, since the patient needs to be injected with radioactive tracers. Dr Koronyo-Hamaoui's team set out to identify a more cost-effective and less invasive technique.
For the study, the researchers conducted a clinical trial on 16 AD patients who drank a solution that includes curcumin, a natural component of the spice turmeric. The curcumin causes amyloid plaque in the retina to "light up" and be detected by the scan. The patients were then compared to a group of younger, cognitively healthy individuals.
The researchers found their results were as accurate as those found via standard invasive methods. Yosef Koronyo, a research associate in the Department of Neurosurgery, said another key finding from the new study was the discovery of amyloid plaques in previously overlooked peripheral regions of the retina.
He said the plaque amount in the retina correlated with plaque amount in specific areas of the brain.
'Now we know exactly where to look to find the signs of Alzheimer's disease as early as possible,' said Koronyo.
Dr Keith L. Black, chair of Cedars-Sinai's Department of Neurosurgery who co-led the study, said the findings offer hope for early detection.
'Our hope is that eventually the investigational eye scan will be used as a screening device to detect the disease early enough to intervene and change the course of the disorder with medications and lifestyle changes,' said Dr Black.
The findings have been celebrated worldwide.
