Alzheimer's disease could be diagnosed with an eye exam

Doctors have found that an ophthalmological examination would reveal which people are at risk of developing Alzheimer's disease years later. A modification of the retina would indeed be a harbinger of brain damage that occurs years before the clinical symptoms. If this type of noninvasive screening is confirmed, it could speed up the therapeutic management.Alzheimer's disease

An annual ophthalmological examination is recommended to detect a possible decrease in visual acuity as well as to detect possible pathologies such as glaucoma or cataracts. And if the latter also allowed to detect the most common form of dementia, Alzheimer's disease?
Using technology similar to that found in many ophthalmologists' offices, researchers at the University of Washington Medical School in St. Louis found how to diagnose this condition in elderly patients with no symptom. Their study, involving 30 patients, was published in the journal JAMA Ophthalmology.

"This technique has the potential to become a screening tool to determine who has to undergo more expensive and invasive tests for Alzheimer's disease before clinical symptoms appear. Says the first author of the study, Bliss E. O'Bryhim. "We hope to be able to use it to find out what people are accumulating abnormal proteins in the brain, which could lead them to develop it years later. Alzheimer's disease is characterized by the appearance of two specific types of lesions, amyloid plaques and neurofibrillary degeneration, each of which is associated with a specific protein compound.

To detect the disease at an early stage

In the first case, it is the amyloid beta protein, naturally present in the brain which, accumulating outside the neurons, forms amyloid plaques. In the second, Tau protein, naturally present in the body, is modified and disrupts the structure of neurons. These brain lesions can occur decades before the onset of symptoms such as memory loss and cognitive decline. One of the research challenges in this area is finding a way to detect the disease as early as possible. Scans and lumbar punctures help doctors to make the diagnosis but these are expensive or invasive.

In previous studies, researchers examined the eyes of people who died of Alzheimer's disease and reported that their eyes showed signs of thinning in the center of the retina and degradation of the optic nerve. In this new work, scientists used a non-invasive technique called "optical coherence tomography" to examine the retinas of 30 participants, 70 years old on average and with no clinical symptoms. This eye test illuminates the eye to measure the thickness of the retina, as well as the thickness of the fibers of the optic nerve and can also distinguish red blood cells from other tissues of the retina.

Same results for classical tests and retina

Conventional screening tests conducted by scientists before the eyes revealed that about half of the participants had high levels of amyloid protein or Tau. However, "in patients with high levels of amyloid or Tau, we detected significant thinning in the center of the retina. Adds the researchers. "We all have a small area devoid of blood vessels in the center of our retina, responsible for our most accurate vision. We also found that this area devoid of blood vessels was considerably enlarged in people with Alzheimer's disease at a preclinical stage. "

Thus, in patients whose classical examinations revealed possible Alzheimer's disease at a preclinical stage, the area in the center of the retina without blood vessels was significantly larger. A peculiarity that suggests a decrease in blood flow: the retina and the central nervous system are so "interconnected" that changes in the brain could be reflected in this part of the eye. If new studies are needed to confirm these results, the researchers hope that this eye test will one day enable people in their forties or fifties to find out if they are likely to suffer from the disease later.

"We know that Alzheimer's disease starts to develop years before the onset of symptoms, but if we could use this test when the disease begins, it may be possible one day for patients to start treatment as soon as possible. to delay the damage. "Conclude the researchers. According to the Health Insurance, Alzheimer's disease is the most common neurodegenerative disease: to date, it affects about 900,000 people in France, including 35,000 people under 65 years old. She estimates that more than one million people will be reached by 2020 given the increase in life expectancy.