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Melanie C W Campbell, Peter A C Neathway, Rachel Redekop, Monika Kitor, Veronica Hirsch-Reinshagen, Ging-Yuek Robin Hsiung, Ian Mackenzie; Two classes of amyloid deposits found in the retina may be differential markers of AMD and Alzheimer's disease. Invest. Ophthalmol. Vis. Sci. 2020;61(9):PP0023.
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Retinal amyloid deposits have been found in both age-related macular degeneration (AMD) and Alzheimer’s disease (AD), both diseases associated with ageing. However, amyloid in AMD is typically found in association with drusen, in posterior retinal layers while our group has found that amyloid deposits in more anterior retinal layers predict the severity of AD pathology in the brain. Here we compare amyloid deposits found in anterior and posterior layers of the retina.
Eyes were obtained from donors, including those with an moderate (n=2) or high severity of AD (n=10) as assessed from brain pathology. Retinas were stained with 0.1% Thioflavin-S, counterstained with DAPI and flat mounted. Retinal deposits were imaged using a fluorescence microscope fitted with a polarimeter. For each deposit, retinal layer was recorded (anterior, n=264; posterior, n=65). From 16 polarimetric images, interactions with polarized light were derived and image texture was assessed via multifractal analysis (MFA). 15 MFA properties were calculated. Using principal component analysis, the polarimetric and MFA variables which explain most of the variance within each group of deposits (anterior and posterior) were determined. These variables were then input into a non-parametric discriminatory analysis to separate and classify deposits by retinal location (anterior or posterior).
Following principal component analysis, 12 polarimetric and 7 MFA properties were retained. Using the 5 nearest neighbours, a non-parametric discriminate analysis was able to discriminate between deposits found in the anterior and posterior of the retina with success rate of 76% (+/-3%) using 4-fold cross-validation.
In conclusion, a combination of polarimetric properties and textural features of retinal amyloid deposits can be used to discriminate between anterior and posterior deposits. This suggests that the properties of deposits found in AMD (expected in posterior layers) and AD (expected in anterior layers) and can be differentiated. Furthermore, an ability to distinguish these two types of retinal amyloid deposits in live-eye imaging would assist their differential classification as associated with AD or AMD pathology. This could improve specificity of diagnosis in each of these conditions.
This is a 2020 Imaging in the Eye Conference abstract.
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