In two studies reported at the Alzheimer's Association International Conference® 2014, the level of beta-amyloid detected in the eye was significantly correlated with the burden of beta-amyloid in the brain and allowed researchers to accurately identify the people with Alzheimer's disease.

Beta-amyloid protein is the primary material found in the sticky brain "plaques" characteristic of Alzheimer's disease. It is known to build up in the brain many years before typical Alzheimer's symptoms of memory loss and other cognitive problems.

In one study, Shaun Frost of the CSIRO (Commonwealth Scientific and Industrial Research Organization, Australia) and colleagues reported preliminary results of a study of volunteers who took a proprietary supplement containing curcumin, which binds to beta-amyloid with high affinity and has fluorescent properties that allow amyloid plaques to be detected in the eye using a novel system from NeuroVision Imaging, LLC, and a technique called retinal amyloid imaging (RAI). Volunteers also underwent brain amyloid PET imaging to correlate the retina and brain amyloid accumulation.

An abstract prepared by the scientists for AAIC 2014 gives the results for 40 participants out of 200 total in the study. The full study is expected to be completed later this year.

Preliminary results suggest that amyloid levels detected in the retina were significantly correlated with brain amyloid levels as shown by PET imaging. The retinal amyloid test also differentiated between Alzheimer's and non-Alzheimer's subjects with 100 percent sensitivity and 80.6 percent specificity.

Furthermore, longitudinal studies on an initial cohort demonstrated an average of 3.5% increase in retinal amyloid over a 3.5-month period of time demonstrating promise of the technique as a means for monitoring response to therapy.

"We envision this technology potentially as an initial screen that could complement what is currently used: brain PET imaging, MRI imaging, and clinical tests," Frost said. "If further research shows that our initial findings are correct, it could potentially be delivered as part of an individual's regular eye check-up. The high resolution level of our images could also allow accurate monitoring of individual retinal plaques as a possible method to follow progression and response to therapy."

The trial is a collaboration between CSIRO, Edith Cowan University, McCusker Alzheimer's Research Foundation and California-based NeuroVision Imaging. The project is part of the Australian Imaging and Biomarkers Lifestyle Study of Aging (AIBL).

In the second study, Paul D. Hartung, M.S, President and CEO of Cognoptix, Inc. and colleagues reported the results of a study of a novel fluorescent ligand eye scanning (FLES) system that detects beta-amyloid in the lens of the eye using a topically-applied ointment that binds to amyloid and a laser scanner.

The researchers studied 20 people with probable Alzheimer's disease, including mild cases, and 20 age-matched healthy volunteers; all participants' Alzheimer's status was masked from the observers. The ointment was applied to the inside of participants' lower eyelids the day before measurement. Laser scanning detected beta-amyloid in the eye by the presence of a specific fluorescent signature. Brain amyloid positron emission tomography (PET) scanning was performed on all participants to estimate amyloid plaque density in the brain.

Using results from the fluorescent imaging, researchers were able to differentiate people with Alzheimer's from healthy controls with high sensitivity (85 percent) and specificity (95 percent). In addition, amyloid levels based on the eye lens test correlated significantly with results obtained through PET brain imaging. No serious adverse events were reported, according to the scientists.

"There is a critical need for a fast, dependable, low-cost and readily available test for the early diagnosis and management of Alzheimer's disease," said Pierre N. Tariot, M.D., Director of the Banner Alzheimer's Institute in Phoenix, and a principal investigator in the study.

"The results of this small Phase 2 feasibility study validate our previously reported results and demonstrate the ability of the FLES system to reproduce the findings of clinical diagnosis of Alzheimer's with high sensitivity and specificity," said Hartung. "This system shows promise as a technique for early detection and monitoring of the disease."

"More research is needed in the very promising area of Alzheimer's biomarkers because early detection is essential for early intervention and prevention, when new treatments become available. For now, these studies reported at AAIC point to possible methods of early detection in a research setting to choose study populations for clinical trials of Alzheimer's treatments and preventions," said Heather Snyder, Ph.D., Alzheimer's Association director of Medical and Scientific Operations.