Purchase this article with an account.
Melanie C W Campbell, Erik Mason, Heqing Huang, Frank Corapi, Laura Emptage, Steven Esau; Linear retardance of retinal amyloid deposits in Alzheimer’s disease. Invest. Ophthalmol. Vis. Sci. 2020;61(7):1850.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Alzheimer’s disease (AD), the most prevalent neurodegenerative disease, is characterized by amyloid-beta in the brain which has been shown to occur in the retina in neural cell layers. In our novel method, polarimetry makes retinal deposits visible and measures their interaction with polarized light. Using a single pass polarimeter, we have shown that retinal amyloid (RA) is birefringent and exhibits linear retardance ex vivo. In polarimetric measurements of the retinal nerve fibre layer (RNFL), retardance measured in vivo in double pass is assumed to be twice that measured in single pass. Here, the retardance values of RA are compared in single and double pass measurements.
This study was conducted in accordance with the Declaration of Helsinki. An eye of a female donor with a diagnosis of AD from the Eye Bank of Ontario was fixed in 10% formalin, then dissected and flat mounted. RA deposits were imaged in single pass with a modified transmission microscope, fitted with a polarimeter. Seven of these deposits were then imaged using a confocal scanning laser ophthalmoscope (double pass) custom fitted with a microscope objective and polarimeter. Mueller matrices were calculated to determine the deposit interactions with polarized light in single and double pass. Measured double pass values were then compared to the linear retardance expected in double pass, predicted from the values measured in single pass.
Across deposits, the average measured double pass retardance was not different from the value predicted from the single pass measurement, with their ratio estimated as 1.04 and a 95% confidence interval= (0.92, 1.15) (Figure). Averages of the ratio of measured to predicted retardance across deposits were not different from 1. Thus the values of double pass retardance for RA deposits were twice the values measured in single pass ex vivo. Values were well above those reported for RNFL.
RA has the potential to be an early, non-invasive biomarker for the presence of AD brain pathology. Retardance measured in vivo in double pass is expected to be twice that measured in single pass and to provide a strong signal and visibility of RA deposits in the living eye.
This is a 2020 ARVO Annual Meeting abstract.
Fit for retardance in degrees measured in double pass vs that predicted from single pass measurements. The slope of 1.04 indicates that the two are not significantly different. Observed retardance values are well above those for the RNFL.
This PDF is available to Subscribers Only