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For The Washington Post 
1 hour ago
Washington – Forget the soul, it turns out the eyes may be the best window to the brain. Changes in the retina may herald Alzheimer’s and Parkinson’s diseases, and the researchers say that an image of your eye could assess your future risk for neurodegenerative disease.
Separated from the brain during embryonic development, the retina contains layers of neurons that appear to undergo neurodegenerative diseases along with their cousins within the skull. The key difference is that these neurons in the retina, against the gelatinous vitreous of the eyeball, live and die where scientists can see them.
Early detection “is kind of a holy grail,” said Ron Petersen, director of the Mayo Clinic Alzheimer’s Disease Research Center and the Mayo Clinic Study on Aging. When a patient complains of memory problems or tremors, the machinery of neurodegenerative disease has probably been at work for years or decades.
Experts liken it to a cancer that only manifests symptoms in Stage 3 or 4. When patients begin to feel the impact of neurodegenerative disease in their daily lives, it is almost too late to receive treatment.
Spotting the warning signs of neurodegenerative disease earlier could give patients more time to plan for the future, whether it’s making arrangements for care, spending more time with family, or writing the great American novel.
In the longer term, researchers hope that the ability to notice brain changes before symptoms begin may eventually lead to more successful early treatments to slow or stop the progress of Parkinson’s and Alzheimer’s disease, as there is currently no such treatment. . The hope is that “the sooner we intervene, the better we will be” in preventing cognitive decline, Petersen said.
While scientists who develop blood tests for Alzheimer’s and Parkinson’s continue to receive the bulk of research funding, retinal exams could be non-invasive, inexpensive and highly sensitive, advocates say.
Alzheimer’s and Parkinson’s cause radical changes in the brain’s landscape before there are behavioral changes: blood vessels atrophy, neurons die prematurely, and misfolded proteins disrupt communication between surviving neurons. Current techniques to detect these changes, including PET imaging at a cost of between $ 3,000 and $ 6,000, can identify Parkinson’s and Alzheimer’s pathology in the brain before symptoms begin, but they are too invasive and expensive for general use. But identifying parallel changes in the retina is a different story.
Maya Koronyo-Hamaoui, a neuroscientist and professor of neurosurgery, studies early intervention and treatment of Alzheimer’s disease at Cedars-Sinai. She and her team have pioneered a technique to visualize plaques associated with Alzheimer’s disease in the neurons of the retina of living patients with mild cognitive impairments, at a cost of about $ 285 per scan. All it requires is modified ophthalmic equipment and lots of curry flavoring.
Patients preparing for the Koronyo-Hamaoui retinal exam are loaded with protein shakes enriched with curcumin, the natural compound that gives turmeric its color and flavor and is central to curries. Curcumin has an extreme affinity for beta amyloid, the protein that forms plaques in Alzheimer’s disease. Surprisingly for those of us who have turmeric in our spice drawers, it also glows yellow when exposed to blue light (yes, you can try this in your spice rack at home). Scientists have linked retinal beta amyloid with lower scores on cognitive tests, more plaque in the brain, and reduced volume in the hippocampus, the brain’s memory center.
If the Koronyo-Hamaoui imaging system seems low-tech to neuroscientists used to radioactive PET tracers and million-dollar scanners, Ruogu Fang’s technique for detecting Parkinson’s is frankly stone age.
Fang is a biomedical engineer who researches applications of artificial intelligence in health and medicine. She and her collaborators at the University of Florida use a fundus camera, a special book-size iPhone accessory, to take high-resolution photos of the microscopic blood vessels at the back of the eye. Changes in the blood vessels of the brain are characteristic of both Parkinson’s disease and Alzheimer’s disease, as a lack of oxygen contributes to the premature death of neurons, and there is strong evidence that the blood vessels of the retina reflect those changes.
Initial results suggest that computer algorithms can use these fundus images to distinguish Parkinson’s patients from healthy controls with better than 70 percent accuracy.
Neither of these biomarkers are perfect candidates: amyloid beta accumulates in the healthy brain with age, and many people with elevated amyloid beta remain cognitively normal, Koronyo-Hamaoui acknowledged. Fang noted that vascular changes are present in a myriad of other conditions, including diabetic retinopathy, a vision condition caused when high blood sugar blocks the blood vessels in the retina and traumatic brain injury.
But it’s not about finding a single miracle biomarker, said Sharon Fekrat, a vitreoretinal surgeon and co-director of Duke’s Retinal Imaging Repository for Neurodegenerative Diseases.
To try to find out which biomarkers are the most effective predictors of Alzheimer’s disease, Fekrat and his colleagues are introducing extensive patient profiles, including images of the retinal vasculature and measurements of the various layers of the retina in people who have known the disease. Alzheimer’s disease, networked, a form of machine learning that identifies patterns based on a set of training data. The network then experiments with different combinations of data points to determine how to get the most accurate diagnosis with the least amount of patient information.
So far, according to Fekrat’s neural network, thinning of the ganglion cell layer of the retina has the highest predictive power for an Alzheimer’s diagnosis; In other words, the neural network was able to use the thickness of a retinal layer to distinguish between patients with clinically diagnosed Alzheimer’s and healthy controls of similar age. That measurement can be achieved using optical coherence tomography, a scanning system of the patient’s eye that most ophthalmologists already use.
Fekrat and the Duke team’s vision is an inexpensive and accessible retinal scan that can identify warning signs of multiple neurodegenerative diseases at the same time. Right now, they’re training their neural network to track images of the retina for the hallmarks of Parkinson’s, Alzheimer’s, and Lewy body dementia, which can cause hallucinations and delusions as dementia develops.
“We could install a machine next to a pharmacy,” Fekrat said. Patients could sit in a booth like the ones with blood pressure cuffs that are already ubiquitous in drug stores, take pictures of their eyes, and “we’ll have our deep learning algorithm analyze it and return a risk score, or index of diagnosis “who can direct them to a neurologist if necessary.
Identifying any of these biomarkers in the retina does not mean that a patient will develop Alzheimer’s or Parkinson’s to its full extent during their lifetime, Petersen said. Such information should be considered a warning sign, such as high blood sugar levels, prompting both the doctor and the patient to be aware of other changes.
It is also an opportunity for the patient to be proactive about preventive measures that can slow the progression of neurodegenerative diseases, such as exercise and an improved diet. “Exercise is the only thing I’ve seen that really helps with Alzheimer’s and Parkinson’s,” said Laura Volpicelli-Daley, assistant professor of neurology at the University of Alabama at Birmingham. He added that he hopes biomarkers that show a patient their personal risk will make the reasons for changing their habits tangible and urgent.
“It’s like 23andMe,” says Fekrat, referring to the popular DNA test that identifies genes associated with a high probability of developing a disease or condition. “When people know their risk, they say, ‘Oh, I have the gene for macular degeneration. I’m not going to smoke.’
The Washington Post
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