Changes to a person's retina could be an early signal of the early stages of Alzheimer's disease, according to a breakthrough international study helped by Australian researchers.
The seven-year international study looked into shared molecular markers and pathways in people with Alzheimer's using a world-first "proteome map", developed by researchers from Australia's Macquarie University.
The map, developed by researchers Vivek Gupta, Mehdi Mirzaei and Stuart Graham, shows the protein-composition of both eyes and the brain, including of those affected by Alzheimer's.
Researchers have known there could be changes in the retina in the early stages of Alzheimer's, but being able to identify this in people had so far proven difficult, Prof Graham said.
The study, published in the National Library of Medicine earlier this year, analysed donor brain and retina tissue from 86 people, developing a proteome map for each person showing how protein changed in their eyes and brains.
The study looked into how two proteins, beta-amyloid and tau, known to build up on the brains of people with Alzheimer's, are also sometimes found within the cells of patient's eyes before they develop symptoms.
Some donors had normal brain function, some had mild impairments, while others had been diagnosed with Alzheimer's disease.
People with the disease had about nine times the beta-amyloid protein in their retina, compared to those without the disease, or with no signs of cognitive impairment.
People who had not been diagnosed with Alzheimer's but had mild cognitive impairment were also likely to have about five times the amount of beta-amyloid protein in their retina, the study found.
It's believed the research could lead to developing a future imaging test, that could detect Alzheimer's disease with a non-invasive eye test.
"We don't have a device in the clinic to identify these changes in a living eye yet; but if we can label these proteins, then develop an imaging device that can spot change at the earliest stages, we may have a way to clinically diagnose diseases such as Alzheimer's," Prof Graham said.
