Choriocapillaris and Retinal Vascular Alterations in Presymptomatic Alzheimer's Disease.

To compare optical coherence tomography angiography (OCTA) retina metrics between cognitively healthy subjects with pathological versus normal cerebrospinal fluid (CSF) Aβ42/tau ratios. Swept-source OCTA scans were collected using the Zeiss PLEX Elite 9000 and analyzed on 23 cognitively healthy (CH) subjects who had previously undergone CSF analysis. Thirteen subjects had a pathological Aβ42/tau (PAT) ratio of <2.7132, indicative of presymptomatic Alzheimer's disease (AD), and 10 had a normal Aβ42/tau (NAT) ratio of ≥2.7132. OCTA en face images of the superficial vascular complex (SVC) and deep vascular complex were binarized and skeletonized to quantify the perfusion density (PD), vessel length density (VLD), and fractal dimension (FrD). The foveal avascular zone (FAZ) area was calculated using the SVC slab. Choriocapillaris flow deficits (CCFDs) were computed from the en face OCTA slab of the CC. The above parameters were compared between CH-PATs and CH-NATs. Compared to CH-NATs, CH-PATs showed significantly decreased PD, VLD, and FrD in the SVC, with a significantly increased FAZ area and CCFDs. Swept-source OCTA analysis of the SVC and CC suggests a significant vascular loss at the CH stage of pre-AD that might be an indicator of a neurodegenerative process initiated by the impaired clearance of Aβ42 in the blood vessel wall and by phosphorylated tau accumulation in the perivascular spaces, a process that most likely mirrors that in the brain. If confirmed in larger longitudinal studies, OCTA retinal and inner choroidal metrics may be important biomarkers for assessing presymptomatic AD.