Proteins in the eye could provide the basis for an accessible, cost-effective test to predict future Alzheimer's disease (AD), according to Boston Medical Centre researchers.

Low levels of amyloid-β and tau proteins in eye fluid were significantly associated with low cognitive scores, according to a new study published in the Journal of Alzheimer's Disease.

Abnormal amounts of amyloid-β and tau proteins are biomarkers of AD, and deposits of amyloid proteins in the brain begin many years prior to symptoms of the disease. Previous research has focussed on measuring these biomarkers in cerebrospinal fluid obtained by lumbar puncture tests. However, lumbar puncture tests are expensive and inconvenient for many patients to undergo.

In this study, researchers tested samples of eye fluid from 80 patients who had undergone eye surgery to determine the levels of amyloid-β and tau proteins, and correlated those levels to the results of a baseline cognitive test. Low levels of these biomarker proteins were significantly associated with lower cognitive scores among the patients, they said.

Diagnosing and starting treatment for AD before symptoms begin is key to managing the disease, because by the time symptoms appear it is often too late for current treatments to have any meaningful effect.

"These findings could help us build an accessible and minimally-invasive test to determine Alzheimer's disease risk, especially among patients with eye disease," said ophthalmology fellow Dr Lauren Wright. "We noted that some of the participants who had low levels of protein biomarkers in their eye fluid already had signs of mild to moderate dementia based on their cognitive scores."

Researchers said these results reaffirmed previous studies suggesting that patients with eye disease were at risk for the development of AD and suggested further investigation in patients with eye disease may yield results that could be generalisable to larger populations.