Abstract Details

Title The Relationship of Amyloid Beta in the Retina to that of the Brain is Burden-specific

Topic Aging, Dementia, and Behavioral Neurology

Presentation(s) P5 - Poster Session 5 (5:30 PM-6:30 PM)

Poster/Presentation
Number 9-024

Objective To test a potential ocular marker of Alzheimer’s disease.

Background The retina is an accessible and well-understood central nervous system structure, making it appealing for the study of disease processes for which the retina parallels brain pathophysiology. This relationship has been proposed for Alzheimer’s disease (AD), which is marked by increased neocortical amyloid beta burden. Although PET image resolution seems prohibitive, we hypothesized that retinal tracer uptake is a detectable fraction of total intraocular PET, and a surrogate for cortical amyloid beta burden, in florbetapir images from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database.

Design/Methods In 92 subjects, we measured peri-retinal intra- and extra-ocular standardized uptake value ratio (SUVR), aided by co-registered T₁-weighted MRI. We compared these data to partial volume corrected SUVRs of cortical grey matter (GM, i.e. amyloid-specific labeling) and white matter (WM, i.e., non-specific labeling) among those with positive PET amyloid burden (Aβ+: cortical SUVR>1.11, n=55). We also compared intraocular SUVR between subjects with the highest GM labeling (Aβ++: cortical SUVR≥1.35, n=32) to those without (Aβ-: n=37).

Results Among Aβ+ subjects, intraocular SUVR was correlated with GM (r₍₅₃₎=0.27,P=0.048, but not WM (P=0.209). Extraocular SUVRs were not correlated with GM (P=0.102), but were correlated with WM (r₍₅₃₎=0.28,P=0.036). There were no significant intra- or extra-ocular differences between Aβ++ and Aβ- groups (P>0.2).

Conclusions Our analyses suggest that retinal signal can be extracted from PET images, and that retinal florbetapir labeling is correlated with cortical amyloid burden. While findings support future exploration of retinal amyloid physiology for in vivo AD studies, histopathological validation is needed. The lack of an inter-group SUVR difference suggests that retinal amyloid burden is lower than in the neocortical GM. However, challenges of PET imaging, including non-specific tracer labeling and low image resolution (relative to retinal thickness), may obscure group differences as partial volume effects admix signal from adjacent tissues.

Authors/Disclosures
David P. Bissig, MD (UC Davis Neurology) PRESENTER	Dr. Bissig has received personal compensation in the range of $100,000-$499,999 for serving as a Physician with University of California - Davis.
	No disclosure on file
	No disclosure on file
	No disclosure on file
Lisa Silbert, MD, FAAN (OHSU)	The institution of Dr. Silbert has received research support from the NIH. Dr. Silbert has received personal compensation in the range of $0-$499 for serving as a Peer Reviewer, study section with NIH.

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