A routine eye exam may be able to screen people for early signs of Alzheimer’s disease, new research has found.
Patients who’ve been diagnosed with the condition have dangerous levels of two rogue proteins in the brain that lead to dementia.
Scientists say these same patients also have thinning of the retina that can be detected through a non-invasive technique that produces high resolution 3-D images of the back of the eyeball.
The test would be performed in middle-age, long before most are diagnosed with Alzheimer’s.
The discovery, from Washington University School of Medicine in St Louis, Missouri, sheds fresh light on the age-related brain disease and could offer hope of earlier diagnosis and treatments that could slow down the progression of symptoms.
Scientists say the eye exam could screen people in their 40s and 50s for Alzheimer’s disease, long before diagnosis. Pictured: Doctors at Washington University School of Medicine screen a patient’s eyes using the technology
To diagnose Alzheimer’s, doctors currently use PET scans, which evaluate your organ and tissue functions, and spinals taps – but they are invasive and often expensive procedures.
An estimated 5.7 million Americans of all ages are living with Alzheimer’s disease in 2018.
Sufferers experience a decline in cognitive, behavioral and physical abilities and there is no cure.
Those who have the disease have a build-up of two proteins, amyloid beta and tau, in the brain that form clumps, which smother and destroy neurons – leading to loss of memory and confusion.
Autopsies of Alzheimer’s patients have also shown a thinning in the retina’s center and deterioration of the optic nerve.
For the study, the team examined the retinas of 30 men and women in their 70s who were participating in the Memory and Aging Project at Washington University’s Knight Alzheimer’s Disease Research Center.
None of the patients had symptoms – such as memory loss, mood and personality changes, and difficulty in understanding questions – but about half had high levels of amyloid or tau proteins, meaning they were at risk of developing the disease.
The researchers used optical coherence tomography angiography (OCTA), which shines a light into the eye and creates 3-D images of blood vessels in the eyes down to the capillary level.
It can also measure the thickness of both the retina and optic nerve fibers.
The team found that the patients who had high levels of the amyloid or tau proteins had significant thinning in the center of their retina.
‘All of us have a small area devoid of blood vessels in the center of our retinas that is responsible for our most precise vision,’ said co-author Dr Rajendra Apte, a professor of ophthalmology and visual sciences at Washington University.
‘We found that this zone lacking blood vessels was significantly enlarged in people with pre-clinical Alzheimer’s disease.
‘The retina and central nervous system are so interconnected that changes in the brain could be reflected in cells in the retina.’
Seventeen of the patients had abnormal PET scans, spinal taps or both – and all of them showed thinning of the retina and enlarged areas without blood vessels in the centers.
In patients with normal PET scans and spinal taps, there was no retinal thinning or enlarged central areas.
Co-author Dr Gregory Van Stavern, a professor of ophthalmology and visual sciences at Washington University, says the eye exam could screen people in their 40s and 50s for the disease, long before diagnosis.
‘We know the pathology of Alzheimer’s disease starts to develop years before symptoms appear,’ he said.
‘But if we could use this eye test to notice when the pathology is beginning, it may be possible one day.’