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Melanie C W Campbell, Ji Ren, Erik Mason, Rachel Redekop, Laura Emptage, Veronica Hirsch-Reinshagen, Robin Hsiung, Ian Mackenzie; Distribution of retinal amyloid deposits in association with Alzheimer’s disease. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3541.
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© ARVO (1962-2015); The Authors (2016-present)
In Alzheimer’s disease (AD), amyloid deposition occurs in both the brain and neural retina. These retinal deposits can be resolved without the use of adaptive optics. Retinal deposits are said to be found preferentially in the far periphery of the retina which could make live eye imaging more complex. Here, we examine the signal strength and location of retinal deposits imaged with polarimetry.
Eyes were obtained from donors, including those diagnosed with AD (n=24) and those not (n=1). The severity of disease was assessed from brain pathology. Retinas were stained with 0.1% Thioflavin-S and counterstained with DAPI, flat mounted in quadrants and imaged using a fluorescence microscope fitted with a polarimeter. Using polarimetry images, linear retardance was calculated. The radial distance from the deposits to the optic nerve head was determined from a subset of data (AD positive n=15, AD negative n=1). Ignoring the far periphery, we sampled deposits in a field of view, consistent with live eye imaging, and tested the prediction of severity of Alzheimer's disease.
Retinal amyloid deposits were seen to have a linear retardance signal up to 6 times stronger than the average background retinal linear retardance signal seen in these experiments and reported in the past.Across 447 deposits with both polarization and Thioflavin signals, deposits occur more frequently in the peripheral retina. However, the number of deposits was found to be directly proportional to the radial distance to the optic nerve head as is the local area of the flat mounted retina. This means that the number of deposits per unit area is approximately constant across the retina. There were slightly more deposits per unit area in the central retina. The number of deposits sampled, ignoring the far peripheral retina, still correlated significantly with the severity of Alzheimer's disease, as previously seen for all deposits.
Retinal deposits which are imaged using polarization are large enough and have a strong enough signal compared to the retinal nerve fibre layer to be resolved in vivo without the use of adaptive optics. Furthermore, in order to predict the severity of Alzheimer's disease, it is not necessary to image deposits in the far periphery of the retina. This will simplify the design of live eye imaging as a diagnostic of AD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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