A routine eye test can detect the earliest stages of Alzheimer’s disease – in seconds, according to new research.
It offers hope of patients being given drugs decades before symptoms develop – when they are most likely to work.
Lifestyle changes, such as eating the right foods and exercising more, may also slow or even halt the condition in those identified at risk.
The non-invasive scan looks for changes in blood vessels in the retina – a coat of light-sensitive cells at the back of the brain.
Tiny alterations in this small piece of tissue mirror those going on in the brain and are the first signs of dementia, say scientists.
The technique called Octa (optical coherence tomography angiography) could revolutionise treatment of the devastating neurological disorder.
Senior author Professor Sharon Fekrat, an ophthalmologist at the Duke Eye Centre in Durham, North Carolina, said: “If we can detect these blood vessel changes in the retina before any changes in cognition, that would be a game changer.”
The study published in Ophthalmology Retina compared the retinas of Alzheimer’s patients, people with mild cognitive impairment (MCI) and healthy controls.
The Alzheimer’s group had loss of small retinal blood vessels at the back of the eye. A specific layer of the retina was also thinner. Even those with MCI did not show this.
The differences in density were “statistically significant” after the researchers took into account other factors such as age and sex.
It demonstrates the imaging device can even distinguish between Alzheimer’s and MCI preliminary forgetfulness that often leads to dementia.
The findings were based on more than 350 participants including 39 with Alzheimer’s, 72 with MCI and 254 who were cognitively healthy.
It is the largest analysis of its kind to date and adds to growing evidence Octa is a potentially vital tool in the war on dementia.
The method has assisted much of the recent research on the eye’s connection with Alzheimer’s.
It enables physicians to see blood vessels in the back of the eye that are smaller than the width of a human hair.
The retina is an extension of the brain and shares many similarities with it suggesting deterioration in one mirrors the other.
They are connected by way of the optic nerve. Prof Fekrat and colleagues said this offers “a window into the disease process.”
Current dementia medications only treat the symptoms – not the cause – meaning there is still no cure. This has led to an increasing focus on prevention.
One of the main reasons new drugs have been ineffective so far is they are administered too late to trial patients – when the disease is advanced.
Early diagnosis will allow researchers to administer them sooner in the disease process which may lead to better results.
It would also give patients time to plan for the future with their families – while they still have their faculties, said the US team.
Prof Fekrat and colleagues said diagnosing Alzheimer’s is a challenge. Some techniques can detect signs of it but are impractical for screening millions of people.
Brain scans are expensive and spinal taps or ‘lumbar punctures’ – in which a needle is inserted into the spine to collect cerebrospinal fluid – have risks.
Instead, the disease is often diagnosed through memory tests or observing behavioural changes – by which time it’s advanced.
Prof Fekrat and lead author Prof Dilraj Grewal, who are based in the same lab, expect their work will one day have a positive impact on patients’ lives.
Prof Fekrat 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’s possible these changes in blood vessel density in the retina may mirror what’s going on in the tiny blood vessels in the brain. Our work is not done.”
She added: “We need to detect the disease earlier and introduce treatments earlier.”
Her results follow a host of recent studies using Octa that have linked eye changes to Alzheimer’s.
The cells of the retina convert light signals coming into the eye into neural signals the brain can interpret.
An earlier study of 32,000 people by University College London using a similar technique found those with thinner retinas were more likely to have problems with memory and reasoning.
Alzheimer’s and other forms of dementia affect 850,000 people in the UK – a figure set to rise to 2 million by 2050 because of the ageing population.
