American scientists found that a quick, non-invasive eye exam might see signs of Alzheimer's disease in a matter of seconds.

The study published on Monday in the journal Ophthalmology Retina showed that the loss of small blood vessels in the retina at the back of the eye were linked with Alzheimer's disease at an early stage.

In people with healthy brains, microscopic blood vessels form a dense web at the back of the eye inside the retina, as seen in 133 participants in a control group, according to the study of more than 200 people at the Duke Eye Center.

However, in the eyes of 39 people with Alzheimer's disease, that web was less dense and even sparse in places than those of people with mild cognitive impairment and healthy people.

The scientists could also distinguish between people with Alzheimer's and 37 participants with mild cognitive impairment, a precursor to Alzheimer's disease.

Early diagnosis of Alzheimer's disease is a huge unmet need since it's not possible for current techniques like a brain scan to screen the number of patients with this disease, said Sharon Fekrat, professor of ophthalmology at Duke.

The eye scan used in the study could reveal changes in tiny capillaries, most less than half the width of a human hair, before blood vessel changes show up on a brain scan, according to the study.

"It's possible that these changes in blood vessel density in the retina could mirror what's going on in the tiny blood vessels in the brain, perhaps before we are able to detect any changes in cognition," said Fekrat.