COPENHAGEN—Amyloid-beta levels in the retina were significantly correlated with amyloid plaque burden in the brain as revealed by PET scans, thus offering a potentially effective eye screening test for the early detection of Alzheimer’s disease, according to research presented at the 2014 Alzheimer’s Association International Conference.
Shaun Frost, a research projects officer at the Commonwealth Scientific and Industrial Research Organization in Clayton South, Australia, and colleagues analyzed 40 volunteers from the Australian Imaging, Biomarkers, and Lifestyle Flagship Study of Aging research cohort at the McCusker Alzheimer’s Research Foundation in Perth, Australia. Between two appointments, the participants took a proprietary curcumin supplement that “binds to amyloid-beta with high affinity and has fluorescence properties that enable amyloid-beta plaques to be imaged in the retina,” noted Mr. Frost.
The investigators performed quantitative analysis of amyloid-beta plaque number, area, and distribution from retinal images to create a retinal amyloid index, and they used blood testing to determine curcumin uptake.
According to the researchers, the retinal amyloid test was able to differentiate between Alzheimer’s disease and non–Alzheimer’s disease with 100% sensitivity and 80.6% specificity.
“The retinal amyloid test is a potential initial screen that could complement currently used brain PET, MRI, and clinical psychometric tests and could potentially be delivered as part of regular eye checks,” stated Mr. Frost. “Micrometer-level imaging resolution could also allow accurate monitoring of individual retinal plaques within Alzheimer’s disease therapeutic trials.”
“My aim now is to develop a low-cost camera that can be utilized and applied,” Professor Ralph Martins, PhD, lead investigator and Chair in Aging and Alzheimer’s Disease, Edith Cowan University and the McCusker Alzheimer’s Research Foundation in Perth, Australia, told Neurology Reviews. “[The goal] would be to combine this eye-imaging technology together with some of the diagnostic blood markers we’re finding to develop sensitivity tests. The work is ongoing, but it’s very exciting. And I see an outcome within the next five years along these lines.”
The full study, which will involve 200 volunteers, is expected to be completed in mid-2014.
Fluorescent Eye Scan May Predict Alzheimer’s Disease
In a second study, a fluorescent eye scan predicted the clinical diagnosis of probable Alzheimer’s disease with high sensitivity and specificity, according to Paul D. Hartung and colleagues.
The researchers used the Fluorescent Ligand Eye Scanning (FLES) System, which noninvasively detects the presence of amyloid-beta in the eye using the combination of a topically applied amyloid binding compound and a laser-based scanner, in 40 participants (20 with probable Alzheimer’s disease and 20 age-matched healthy volunteers). The fluorescent ligand was formulated into an ophthalmic ointment and dosed topically to the inside of the lower eyelid in subjects the day before measurements were taken.
The device detects a fluorescent signature that is characterized by the lifetime measurement of the ligand bound to amyloid-beta in the supranucleus region of the human lens, explained Mr. Hartung, President and CEO of Cognoptix in Acton, Massachusetts. In addition, amyloid PET imaging sessions were conducted with florbetapir to estimate the amyloid-beta plaque density in the participants’ brains.
The researchers found that the patients with Alzheimer’s disease and healthy volunteers were differentiated with a sensitivity of 85% and specificity of 95%. In addition, FLES showed a strong correlation with amyloid PET imaging.
“The results in the eye show significant correlation with that obtained by amyloid brain imaging using florbetapir,” stated Mr. Hartung. “The clinical study was conducted with no serious adverse events related to the use of the fluorescent ligand or the laser scanning device in the eye.”
—Colby Stong