Retinal Microvascular Alterations in Alzheimer's Disease and Mild Cognitive Impairment
Background: The retina and brain share many neuronal and vasculature characteristics developmentally and potential biomarkers may be present in the retina. We investigated the retinal microvasculature in Alzheimer's disease (AD) and mild cognitive impairment (MCI) using optical coherence tomography angiography (OCTA).Methods: In this cross-sectional study, 24 AD participants, 37 MCI participants, and 29 controls were diagnosed according to internationally accepted criteria. OCTA images of the
... CTA images of the superficial and deep capillary plexus (SCP, DCP) of the retinal microvasculature were obtained using a commercial OCTA system (Zeiss Cirrus HD-5000 with AngioPlex, Carl Zeiss Meditec, Dublin, CA). The main outcome measures were vessel density (VD) and fractal dimension (FD) in the SCP and DCP within a 2.5-mm ring around the fovea were compared between groups. Perfusion density of large vessels and foveal avascular zone (FAZ) area were additional outcome parameters.Results: Age, gender and race did not differ among groups. However, there was a significant difference in diabetes status (P=0.039), and systolic blood pressure (P=0.008) among the groups. After adjusting for confounders, AD participants showed significantly decreased VD in SCP and DCP (P = 0.005 and P = 0.016, respectively) and decreased FD in SCP (P = 0.008), compared to controls. MCI participants showed significantly decreased VD and FD only in SCP (P = 0.005 and P < 0.001, respectively) and not the DCP (P > 0.05) compared with controls. There was no difference in the OCTA variables between AD and MCI (P > 0.05). Perfusion density of large vessels and FAZ area did not differ significantly between groups (P > 0.05).Conclusions and relevance: Eyes of patients with AD have significantly reduced macular VD in both plexuses whereas MCI participants only showed reduction in the superficial plexus. Changes in the retinal microvasculature and capillary network may mirror small vessel cerebrovascular changes in AD.