Alzheimer’s disease may soon be spotted through a simple eye test, after scientists discovered tell-tale alterations in the retina and blood vessels when dementia is present.
Currently diagnosing Alzheimer’s is tricky, requiring an expensive brain scan, a risky spinal tap or in most cases a behavioural assessment by a doctor based on symptoms.
But US scientists at the Duke Eye Centre in North Carolina, wondered if changes might also be visible in the retina, which is an extension of the brain and so could offer a window into what is happening behind the skull.
The retina’s job is to convert light into neural signals which it sends to the brain to be processed into understandable images.
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, compared to healthy people and those with mild cognitive impairment (MCI), a forerunner to dementia.
The team is hopeful that dementia could be picked up early, before symptoms are present, when there still may be time to reverse or halt the disease through medication or lifestyle changes. And unlike other tests, a diagnosis could be made within just a few minutes.
“Early diagnosis of Alzheimer's disease is a huge unmet need,” said Dr Sharon Fekrat, Professor of Ophthalmology at Duke. “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.
“If we can detect these blood vessel changes in the retina before any changes in cognition, that would be a game changer.”
Around 850,000 people suffer from dementia in Britain, and the majority will have Alzheimer’s disease. Yet despite decades of research, costing billions of pounds, there is still no cure or medication to alleviate symptoms.
Many experts now believe that trials into new drugs have failed because once damage is done to the brain it is irreversible and so catching the disease early is the key to preventing the devastating effects.
The new test uses non-invasive imaging called optical coherence tomography angiography (OCTA).
For their study, researchers used OCTA to compare the retinas of 39 Alzheimer's patients with 72 37 people with mild cognitive impairment, and 133 cognitively healthy people.
Dr James Pickett, Head of Research at Alzheimer’s Society, said: “We urgently need a test to identify people who might go on to develop dementia, but who aren’t showing any clinical symptoms yet.
“The very earliest changes in the brain can appear up to 20 years before we see clinical symptoms, so the holy grail would be to identify and treat people the moment these changes start.
“With one million people predicted to develop dementia by 2021, and no cure for the condition, any breakthroughs in early diagnosis could make a huge difference.”
Dr Rosa Sancho, Head of Research from Alzheimer’s Research UK said added: “The eye offers a unique opportunity to look at brain changes in a way that is not invasive.”
The research was published in the journal Opthamology Retina.