Presently, diagnosis of Alzheimer’s disease begins with symptoms patients exhibit, namely memory loss. Unfortunately, by the time patients become symptomatic, the disease has already progressed to its later stages. Like age-related macular degeneration, treating Alzheimer’s disease at such an advanced stage is difficult, if not altogether impossible. However, recent advances in Alzheimer’s research have yielded the potential for a method of detecting the disease in its developmental stages, possibly decades before patients become symptomatic.
What is now generally agreed upon by neurologists as being a biomarker of Alzheimer’s disease (AD) is the presence of amyloid beta protein deposits in the brain. Moreover, amyloid also accumulates in the eye, and it has been theorized that if a correlation can be made between the amyloid in the eye and the amyloid in the brain, it would be possible to diagnose AD by looking into the eye.
Retinal Amyloid Index
Acting on this theory, two companies, Cognoptix and NeuroVision, have been developing simple tests to detect amyloid beta plaques in the eye. The Retinal Amyloid Index (NeuroVision), a working title for the test, utilizes a device that looks and functions similarly to a conventional retinal imaging scanner and a curcumin compound, administered orally to the patient, to detect amyloid plaques in the retina, according to Keith L. Black, MD, chairman and professor of the Department of Neurosurgery at Cedars-Sinai Medical Center in Los Angeles, Calif., and co-founder of NeuroVision.
Amyloid in the retina may help detect Alzheimer’s disease early, according to Keith L. Black, MD.
Image: Cedars-Sinai Medical Media
Curcumin, the active ingredient in turmeric, or curry, crosses the blood-brain and blood-retina barrier and binds with high affinity to amyloid beta plaque — particularly amyloid beta 42, which is the most toxic. Curcumin is also a fluorochrome and naturally generates a fluorescent signal, so once bound to the amyloid plaques, the fluorescing curcumin signals are then captured by the retinal imaging device, Black explained during a Google “Solve for X” presentation.
“An increase in fluorescence that we can detect with the retinal imager is directly proportional to the amount of amyloid protein in the back of the eye, which correlates with the amount of amyloid protein in the brain,” Black said in an interview.
Through digital processing of the increased fluorescence and the application of quantitative algorithms, Black and his colleagues have developed a way to heat-map the data and refine it into a quantitative value, a Retinal Amyloid Index number, he said during the online presentation.
The hallmark of AD, according to Black, is the accumulation of amyloid beta proteins in the brain, which may begin about 20 years before a person develops memory loss symptoms.
“Most people, if they’re going to get AD, start developing the pathology hallmarks, such as amyloid deposits, in their 50s,” he said. “It’s the first thing that changes.
“The whole key for having an effective treatment for AD is early detection. You want to prevent those brain cells from being killed or dying in the first place. This test allows us to detect the onset of AD years, maybe even decades, before one develops memory loss. That gives us a much better probability of having an effective treatment for it,” he said.
Black said this test has the potential to be included as part of a routine eye exam for all patients older than 50.
“A PET scan is about a $5,000 test and radioactive,” he said. “With the Retinal Amyloid Index, we’re looking at a $500 test that performs at the micron level of resolution, instead of the millimeter-level performance with a PET scan. It is more sensitive than PET, less costly, noninvasive and safe.”