Why eyes are a window to dementia: Yellow spots and thicker blood vessels underneath the retina could be early warning signs of the brain disease, study finds
- Hard drusen – fat and calcium buildups in the eye – could be a sign of dementia
- Scientists found them in 25% of Alzheimer’s patients, but 4% of healthy people
- Thickened blood vessels could point to a poor blood supply to the brain
- Experts hope eye scans could offer a window into brain disease
Tiny yellow spots in the back of the eye could be an early warning sign of dementia, new research suggests.
The spots, called ‘hard drusen’, are small deposits of fat and calcium that form in a layer underneath the retina and can be seen in scans.
The spots are a common symptom of ageing and often seen in people over 40, and they have long been thought to be harmless.
But new research from Queen’s University in Belfast, shows how Alzheimer’s sufferers have many more of the yellow or white hard dots than healthy people.
The study also suggests changes in blood vessels in the eye could be linked to the development of dementia.
Scientists say scanning for the spots and examining the eye’s blood vessels could be a ‘valuable tool in Alzheimer’s disease monitoring’.
Researchers hope eye scans could be a cheaper way of detecting brain disease plus, they say, they are quicker and less invasive
David Allamby, laser eye surgeon and medical director of London’s Focus Clinic said: ‘The eyes have long been thought of as a window to the body, where the health of the eye is a reflection of the general health of the person.
‘You can often detect the early signs of heart disease, diabetes and even brain tumour through a simple eye test.
‘And the eye’s retina is part of the central nervous system, and shares many structural and functional features with the brain.
‘So examining the eye could therefore be a monitoring tool for the changes in the brain also.’
The study was led by Queen’s University’s Dr Imre Lengyel whose team scanned the eyes of 117 patients aged between 60 and 92.
A quarter of people with Alzheimer’s have the yellow spots
He discovered 25 per cent of patients with Alzheimer’s have the yellow spots behind their eyes, compared with just found per cent of those without the disease.
While hard drusen are considered to be harmless, soft drusen are known to be a risk factor for developing age-related macular degeneration, which is vision damaging.
Researchers also found people with Alzheimer’s have thicker blood vessels in their eyes, slowing blood flow.
They say this could be a warning sign for vascular dementia, in which the brain declines because of reduced blood flow.
Eye scanning cheaper than brain scans
Dr Lengyel 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.
HOW LOUD MUSIC AND DEPRESSION COULD ALSO RAISE DEMENTIA RISK
Two studies released this week suggested that both depression and hearing loss – even if it is very minor – can raise a person’s risk of getting dementia.
Scientists from the University of Sussex and Ohio State University, in separate studies, found hearing loss and depression both age the brain prematurely.
The US researchers found that even a subtle hearing loss – such as that caused by loud music or power tools – could make a person’s brain work harder to understand what it hears.
People will slight deafness were found to use both sides of their brain to hear, whereas people with normal hearing only use one side.
This, the scientists say, could ‘drain’ the brain’s resources before it gets to old age.
Scientists in the UK, meanwhile, found people who suffer from depression show a faster decline in brain power as they get older, whether they are diagnosed with dementia or not.
Both teams said they hope the findings will help people take better precautions by protecting their hearing and seeking help for mental health problems.
‘It’s also about finding cheaper methodologies.
‘Brain scanning costs thousands of pounds per scan. And you can’t perform scans often because they use radioactive tracers which can be harmful to the body.
‘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.’
There are 850,000 people with dementia in the UK, with numbers set to rise to over a million by 2025, according to the Alzheimer’s Society.
Alzheimer’s disease is the most common type of dementia, affecting 62 per cent of those diagnosed.
Other types of dementia include vascular dementia, which affects 17 per cent of patients, and mixed dementia which affects 10 per cent of those diagnosed.
How the research was carried out
Dr Lengyel and his team used state-of-the-art ultra-widefield (UWF) retinal imaging scanning equipment on a group of 117 patients from west London.
They ranged in age from 60 to 92 years old, and 56 of them had Alzheimer’s while 48 acted as ‘controls’ for the experiment.
He discovered that one in four of the Alzheimer’s patients had hard drusen, but only one in 25 of those without the disease had them.
Dr Lengyel said: ‘At the two-year follow up examination conducted on those who were still able to comply, we found that there were more areas associated with drusen deposition in Alzheimer’s disease.
‘But we also observed a consistently higher increase in drusen numbers in all patients when compared to controls.’
Thicker blood vessels could point to bad blood flow to the brain
In his study Dr Lengyel also found people with Alzheimer’s have thicker blood vessels in their eyes.
He revealed: ‘The team were able to use imaging to measure the thickness of the vessels in the eye.
‘What they found was that in Alzheimer’s disease patients there are measurably thicker vessels.
‘And if the vessels widen, then the blood flow slows down.
‘Our gut feeling is that the eye is mirroring what’s occurring in the brain. Although it’s not exactly the same, it’s the same type of change.’
Writing in the journal Ophthalmic Research he added: ‘If the observations made in this initial study remain robust, then routine UWF imaging might achieve an earlier and thereby clinically opportune and cost-effective method for monitoring the progression of Alzheimer’s disease and identifying individuals at a high risk of developing Alzheimer’s disease.’
Symptoms of dementia include memory loss, confusion and problems with speech and understanding. Dementia is a terminal condition.
Roughly one in six people over the age of 80 have dementia – but there are also more than 40,000 people under 65 with dementia in the UK.
There is currently no cure for Alzheimer’s disease, but there is medication available that can temporarily reduce the symptoms.
Early intervention is critical
David Allamby added: ‘Previous studies looking at the relationship between the eyes and Alzheimer’s had looked at a protein known as beta-amyloid plaque.
‘Research showed that elevated levels of this biomarker was a precursor for dementia, with Alzheimer’s sufferers having more than twice as much of this protein in their retinas as non-sufferers.
‘This new study instead looks at hard drusen as a biomarker, found in a different area of the eye.
‘It could prove valuable indeed when it comes to predicting Alzheimer’s, particularly as early medical intervention is so critical when it comes to treating this terrible condition.’
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