They say the eyes are the windows to the soul, but are they also a Magic 8 Ball for Alzheimer’s? Scientists have found that they’re able to see signs that Alzheimer’s may be lurking in the eyes of those who also have the biomarkers of the disease in their brains. A diagnostic tool like this could help to treat patients before they’ve even developed symptoms, which many scientists now believe is crucial to stopping the disease in its tracks before the damage to the brain is too great.
Scientists have looked at the eyes to measure beta-amyloid, the toxic protein that accumulates in Alzheimer’s before. But this group of researchers, from Washington University in St. Louis, was able to verify that those who had other, easily measurable abnormalities in their retina also had signs of Alzheimer’s in the brain. Those patients have what is called preclinical Alzheimer’s—signs of Alzheimer’s in the brain, but no symptoms like memory loss.
Right now, diagnosis and treatment only begins when a person has symptoms, which typically occur after the age of 65. But recently, researchers have collectively come to the conclusion that delivering drugs to those who already have the symptoms of Alzheimer’s is too late—their brain is already too ravaged by the disease for the drugs to have an effect. Many attribute Alzheimer’s drugs’ high failure rate to the fact that they are usually only tested on people who are already showing symptoms of the disease—even though there is evidence that the build up of beta-amyloid, the toxic protein associated with the disease, starts in the brain decades earlier.
In this study, scientists looked at the eyes of 30 people, around half of whom had preclinical Alzheimer’s. The other half acted as a control. When they peered into their eyes, they were able to see that those who had signs of Alzheimer’s in the brain also had common differences in their eyes when compared to the control group. They used technology called optical coherence tomographic angiography (OCTA), which uses light to measure the blood flow patterns within the eyes, along with retinal thickness.
In the patients with preclinical Alzheimer’s, there was an area in the center of the retina that was much thinner with fewer blood vessels in comparison to those without signs of Alzheimer’s in the brain.
The OCTA uses a machine that most eye doctors already have in their offices. An early detection test like this could happen alongside a yearly eye exam, helping to identify the best candidates for clinical trials aimed at reducing toxic proteins in the brain before symptoms appear.
The test itself takes around five minutes, and nothing touches the eye, according to study authors. Comparatively, a PET scan or spinal tap, currently the only ways to measure beta-amyloid build-up in the brain, is a long process that requires a patient to sit in a machine or endure prodding with a needle in the lower back. Both are less than ideal.
“It is important to identify people with early-stage Alzheimer’s disease who could potentially benefit from treatment but current testing to do this is invasive and expensive,” wrote the study authors.
While this study was small, with just 30 participants, researchers hope to continue to conduct studies to see if the eye abnormalities hold true for a larger and more varied group of people.
This study was published in the journal JAMA Opthalmology.