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Fred N. Ross-Cisneros, Samuel Asanad, Ernesto Barron, Alec Chan Golston, Eric A Barron, Alfredo A Sadun; Morphological Changes of the Retinal Choroid in Severe Alzheimer’s Disease: A Histopathological Study. Invest. Ophthalmol. Vis. Sci. 2018;59(9):306.
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© ARVO (1962-2015); The Authors (2016-present)
The choroid exhibits significant thinning in Alzheimer's Disease (AD) as measured in vivo using optical coherence tomography (OCT). This study aims to histopathologically confirm these findings by performing a morphological analysis of the choroidal area in severe AD using postmortem tissue. We hypothesize that the degenerative effects of AD will produce a significant reduction in choroidal thickness.
5 AD postmortem eyes (mean age: 86.2±15.10 years) were compared to 5 age-matched controls (mean age: 84.8±14.75 years). Tissues were fixed in phosphate-buffered formalin, dissected horizontally through the middle of the optic nerve, embedded into paraffin, sectioned and stained with hematoxylin and eosin. Choroidal thickness was measured from the posterior border of the retinal pigment epithelium (RPE) to the anterior sclera. Measurements were performed at 18 different points along the horizontal meridian beginning from the edge of the optic disc at 100 and 500 μm intervals spanning a total distance of 4.5 mm in both nasal and temporal directions. Welch’s t-test was used for statistical analysis.
Mean total choroidal thickness in the nasal region was significantly thinner in AD (1187.60 ± 9.34μm) compared to controls (1545.77 ± 14.82μm; p< 0.0001). Nasal thinning in AD was found to be most severe between 2.5 to 3.5mm from the optic disc edge. On the contrary, in the temporal region, mean choroidal thickness was significantly larger in AD relative to controls, specifically in the perimacular region (829.77 ± 18.85μm in AD and 678.08 ± 11.24μm in controls; p=0.01). Qualitatively, the large vessel layer of the choroid in the temporal region was observed to be larger in AD relative to controls, especially in the perimacular region.
Choroidal thinning was topographically confirmed in the nasal region and is consistent with clinical OCT studies in mild to moderate AD patients. Importantly, the choroid in severe AD was significantly thicker in the perimacular region, where the retina is reportedly most atrophic. These findings support the role of vascular factors in AD pathogenesis and correlate vessel layer changes in severe disease stages.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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