Significant brain damage from Alzheimer’s disease can occur years before symptoms such as memory loss and cognitive decline appear. Scientists estimate that Alzheimer’s-related plaques can build up in the brain two decades before the onset of symptoms, so researchers have been looking for ways to detect the disease sooner. Currently, physicians use PET scans and lumbar punctures to help diagnose Alzheimer’s, but these tests are expensive and invasive.

GREGORY VAN STAVERN, MD, (SEATED) AND RAJENDRA APTE, MD, PHD, EXAMINE KATHLEEN ESTERHOLD’S EYES USING TECHNOLOGY THAT ONE DAY MAY MAKE IT POSSIBLE TO SCREEN PATIENTS FOR ALZHEIMER’S DISEASE DURING AN EYE EXAM.
Photo by Matt Miller, Washington University School of Medicine

In previous studies, researchers examining the eyes of people who had died from Alzheimer’s observed signs of thinning in the center of the retina and degradation of the optic nerve. That clue led researchers at Washington University School of Medicine to embark on a new study that considered a noninvasive eye test called optical coherence tomography angiography as a possible tool for detecting Alzheimer’s.

In the study, researchers examined the retinas of 30 people with an average age in the mid 70s, none of whom exhibited clinical symptoms of Alzheimer’s. These participants were patients in The Memory and Aging Project at the university’s Knight Alzheimer’s Disease Research Center. About half of the participants had elevated levels of the Alzheimer’s proteins amyloid or tau as revealed by PET scans or cerebrospinal fluid, suggesting that although they didn’t have symptoms, they likely would develop Alzheimer’s. In the other participants, PET scans and cerebrospinal fluid analyses were normal.

The test used in the study shines light into the eye, allowing a doctor to measure retinal thickness, as well as the thickness of fibers in the optic nerve. A form of this test often is available in ophthalmologists’ offices. For this study, however, researchers added a new component to the more common test: angiography, which helps distinguish red blood cells from other tissue in the retina and looks at blood-flow patterns.

THIS TECHNIQUE HAS GREAT POTENTIAL TO BECOME A SCREENING TOOL THAT HELPS DECIDE WHO SHOULD UNDERGO MORE EXPENSIVE AND INVASIVE TESTING FOR ALZHEIMER’S DISEASE PRIOR TO THE APPEARANCE OF CLINICAL SYMPTOMS.

The study’s testing revealed that each of the participants with elevated levels of amyloid or tau also had significant thinning in the center of the retina, says co-principal investigator Rajendra Apte, MD, PhD, a Washington University ophthalmologist at Barnes-Jewish Hospital. In addition, the test showed that each of them also had an area in the center of the retina that was significantly enlarged. “The retina and central nervous system are so interconnected that changes in the brain could be reflected in cells in the retina,” Apte says. Retinas appeared normal in the other people whose PET scans and cerebrospinal fluid analyses were within the typical range.

More studies are needed to replicate this study’s findings, says Gregory Van Stavern, MD, a Washington University neuro-ophthalmologist at Barnes-Jewish Hospital and the study’s other co-principal investigator. And he notes that if changes detected with the eye test can be used as markers for Alzheimer’s risk, it may be possible to screen people as young as their 40s or 50s to see whether they are at risk for the disease. According to resident physician Bliss O’Bryhim, MD, PhD, first author of the study, “This technique has great potential to become a screening tool that helps decide who should undergo more expensive and invasive testing for Alzheimer’s disease prior to the appearance of clinical symptoms.” Van Stavern adds, “We know the pathology of Alzheimer’s disease starts to develop years before symptoms appear, but if we could use this eye test to notice when the pathology is beginning, it may be possible one day to start treatments sooner to delay further damage.”

Originally published by Washington University School of Medicine at medicine.wustl.edu/news