By Daniel J. McLaughlin
A "game changer" may have been found in detecting Alzheimer's disease.
US scientists believe they have discovered a link between thinner retina and people with dementia. This potentially means an eye test could be used to spot the disease in early stages.
However, the NHS warns that it is "too soon to say" whether a simple test could be used to diagnose Alzheimer's disease.
Alzheimer’s disease could be spotted through a simple eye test, the Daily Telegraph reports. A US study has found that there could be "tell-tale alterations in the retina and blood vessels" when dementia is present.
Dr Sharon Fekrat, professor of ophthalmology at the Duke Eye Centre in North Carolina, said that the visible changes could be a "game changer".
She said: "Early diagnosis of Alzheimer's disease is a huge unmet need. It's not possible for current techniques like a brain scan or lumbar puncture to screen the number of patients with this disease.
"It is possible that these changes in blood vessel density in the retina may mirror what's going on in the tiny blood vessels in the brain, perhaps before we are able to detect any changes in cognition."
Dr Fekrat added: "If we can detect these blood vessel changes in the retina before any changes in cognition, that would be a game changer."
The retina is an extension of the brain and "could offer a window into what is happening behind the skull".
The US scientists found that the retina was thinner in people with Alzheimer's, and they had also lost more small blood vessels at the back of the eye.
While it is easy to jump to conclusions following the study, NHS Behind the Headlines warns that it is "too soon to say" that it will lead to a simple test to diagnose Alzheimer's disease.
They explain: "The research doesn't tell us whether the retinal changes occurred before or after Alzheimer's set in. And we don't know that the changes are unique to Alzheimer's.
"They might also be seen in people with other types of dementia, medical conditions like diabetes, or other eye conditions."
The media coverage has been guilty of "over-optimistic reporting". They also criticise the Daily Mail and the Sun for suggesting that the eye test could detect changes before symptoms appear, "which is wrong and not supported by this research".
The NHS explains that it was a cross-sectional study that measures changes at a particular point in time. This means that we cannot judge what came first: the retinal changes or the onset of Alzheimer's.
They suggest: "It would be valuable to follow over time people with Alzheimer's and with MCI [mild cognitive impairment, a forerunner to dementia] - where the blood vessel changes aren't currently seen - to see whether things progress or change."
According to the Alzheimer's Society, there are 850,000 people with dementia in the UK, with numbers set to rise to over one million by 2025. This will rise to two million by 2051.
It is estimated that 225,000 people will develop dementia this year - that's one in every three minutes.
There is currently no cure or medication to help with the symptoms of dementia.
Alzheimer's disease is the most common cause of dementia. It affects around six in every 10 people with dementia.
The majority of people who develop Alzheimer's disease are over the age of 65. Symptoms include: memory loss, confusion, and problems with speech and understanding. It is a terminal condition.