A study featured at the Alzheimer's Associationx®International Conference 2011 in Paris explored whether characteristics of blood vessels in the retina might serve as possible biomarkers for Alzheimer's disease.

While most Alzheimer's-related pathology occurs in the brain, the disease has also been reported to create changes in the eye, which is closely connected to the brain, and more easily accessible for examination in a doctor's office.

"Today, there is no single method for detecting Alzheimer's until the disease is well advanced. Current PET and MRI scans can detect some brain changes, but these procedures can be expensive and technically challenging, and so are impractical for testing in large populations," said Shaun Frost, MSc, of CSIRO's Australian e-Health Research Center.

In a small pilot study, Frost and colleagues examined retinal photographs of people with Alzheimer's (n=13), mild cognitive impairment (n=13) and healthy participants (n=110) from the larger Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL). They examined a variety of parameters, including the width of retinal blood vessels.

They found that the width of certain blood vessels in the back of the eye were significantly different for people with Alzheimer's vs. healthy controls, and that this correlated with a brain imaging benchmark indicative of Alzheimer's disease - the deposition of amyloid plaque in the brain as measured by PET PiB imaging.

"Our studies are very preliminary, but encouraging," said Frost. "Since amyloid plaque build up in the brain occurs years before cognitive symptoms of Alzheimer's are evident, a non-invasive and cost-effective retinal test may hold promise as an early detection tool for the disease. We hope that, in the future, our measure could be used with blood-based tests to help doctors identify who needs further assessment with PET imaging and MRI for Alzheimer's, but more research is needed."