Fluorescent imaging approaches show potential for early Alzheimer's detection

Examinations of the eye involving fluorescent imaging could indicate the build-up of beta-amyloid, a protein associated with Alzheimer's, in the brain, according to the results of two research trials reported at the Alzheimer's Association International Conference 2014 (AAIC 2014; held July 12-17, 2014, in Copenhagen, Denmark).

Related: Noninvasive approach to Alzheimer's assessment promises early diagnosis

At AAIC 2014, Paul D. Hartung, M.S, president and CEO of Cognoptix (Acton, MA), 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.

Also at the conference, Shaun Frost of the Commonwealth Scientific and Industrial Research Organization (CSIRO; Clayton, South Victoria, 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 (Sacramento, CA), and a technique called retinal amyloid imaging (RAI). Volunteers also underwent brain amyloid PET imaging to correlate the retina and brain amyloid accumulation.

Preliminary results of the study 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 percent 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.

Frost says that with further research, their imaging method could potentially be delivered as part of an individual's regular eye check-up. The high resolution level of their images could also allow accurate monitoring of individual retinal plaques as a possible method to follow progression and response to therapy, he adds.

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