According to the researchers, yellow spots also known as "hard drusen" in the eye could be an early indicator of dementia.

Hard drusen is made of fat and calcium deposit that form in a layer underneath the retina and can be seen in scans. A common signs of ageing, the spots have long been thought to be harmless. But, the findings showed that 25 per cent of people with Alzheimer's have more number of such spots compared to four per cent of healthy people. "We found that there were more areas associated with drusen deposition in Alzheimer's disease," lead author Imre Lengyel from Queen's University in Belfast, Northern Ireland, was quoted as saying to the DailyMail.

The results also showed that, people with Alzheimer's had thicker blood vessels which may slow down the blood flow. Thus, scanning for the spots and examining the eye's blood vessels could be a valuable tool in Alzheimer's disease monitoring, the researchers said. "A brain disease is difficult to diagnose through the eye. But we can use ophthalmologic imaging to chart progression of the disease and monitor the effectiveness of medications used to combat it," Lengyel added.

"An eye imaging session would comprise 20 seconds of time and is very non-invasive. It's exciting. We really hope that eye imagining will be a powerful tool in monitoring Alzheimer's progression." In the study, published in the journal Ophthalmic Research, the team conducted eye test on 117 patients aged between 60 to 92 years. The researchers hope that the study may be helpful in early detection of dementia so that early precaution is taken in order to combat the disease.