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Tao Jin, Laura Emptage, David DeVries, Monika Kitor, Melanie C W Campbell; The effects of amyloid-β deposits on retinal tissue assessed from polarization properties. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3367.
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© ARVO (1962-2015); The Authors (2016-present)
Alzheimer’s disease (AD) is a neurodegenerative disease with characteristic deposition of amyloid-β (Aβ) in the brain and definitive diagnosis only after death. Our group and others have found Aβ deposits in the retina. Here, we analyze the structure of these deposits and nearby retinal layers.
Eyes were obtained in compliance with the Declaration of Helsinki from four donors diagnosed with AD. The retinas are flat mounted and stained with 0.1% Thioflavin-S and DAPI. Fluorescence confocal microscopy and thickness modelling are used to create 3D models of amyloid plaques and surrounding retina. Mueller matrix polarimetry was used to image 28 deposits found in the confocal microscope. The polarization properties of the deposits and the retina were calculated using matrix decomposition pixel by pixel. Registration of the confocal images and the polarization images was based on multimodal registration and the birefringence was then calculated pixel by pixel.
The average linear retardance of the deposits is higher than the surrounding retina; however, there are some areas with lower retardance. Some of these lower retardance regions have thin deposits. This indicates thinning in the retinal nerve fiber layer (RNFL). In these areas there is also a loss of ganglion cells. In regions where the deposits are thicker, low retardance results in a calculated lower birefringence. The orientation of the fast axis of linear retardance across the deposits is consistent with both results.
The polarization properties of the deposits differentiate them from the surrounding retina. The thinning of the RNFL and the loss of the ganglion cells are consistent with local damage from Aβ. This result may explain the thinning of the RNFL previously measured in AD patients. Lower birefringence within the deposits indicates possible disorder of the amyloid fibrils.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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