Inner Retinal Optical Coherence Tomography Angiography Metrics in Pre-Alzheimer’s Disease

Abstract

Purpose : To compare optical coherence tomography angiography (OCTA) in the inner retina between subjects with pathological versus normal cerebrospinal fluid (CSF) Aβ42/Tau ratios.

Methods : Swept-source (SS-)OCTA from a total of 23 subjects who underwent CSF analysis and imaged on the Zeiss Plex Elite 9000 (6x6 mm; 1024x1024 pixels, foveal centered) were analyzed in this post-hoc analysis. None of the subjects showed mild cognitive impairment (MCI) or Alzheimer's disease (AD). Based on criteria by Harrington et al. (PLOS One 2013), subjects with a CSF Aβ42/Tau ratio ≥ 2.7132 were defined to have a normal Aβ42/Tau (NATs) ratio and those below this cut-point were defined to have a pathologic Aβ42/Tau (PATs) ratio associated with higher risk for developing MCI or AD. En face OCTA slabs of the superficial vascular complex (SVC) and deep vascular complex (DVC) were binarized and skeletonized using Image J in order to quantify the perfusion density (PD, %), vessel length density (VLD, %) and fractal dimension (FD, n) within the entire 6x6 mm scan area, and within 3-mm and 6-mm rings of the ETDRS grid. The area of the foveal avascular zone (FAZ, mm2) was calculated using the SVC slab. Mean measurements between PATs and NATs were compared using t-test.
Results: 10 subjects were classified as NATs and 13 as PATs based on the CSF biomarkers. PD%, VLD % and FD within the SVC in the eyes of PATs were significantly lower compared to NATs. The FAZ area was also enlarged in the eyes of PATs vs. NATs (p=0.027). (Table 1) In contrast, mean PD%, VLD% and FD for the DVC were not significantly different (p>0.05) between PATs and NATs. (Table 2)

Results : 10 subjects were classified as NATs and 13 as PATs based on the CSF biomarkers. PD%, VLD % and FD within the SVC in the eyes of PATs were significantly lower compared to NATs. The FAZ area was also enlarged in the eyes of PATs vs. NATs (p=0.027). (Table 1) In contrast, mean PD%, VLD% and FD for the DVC were not significantly different (p>0.05) between PATs and NATs. (Table 2)

Conclusions : The decreased PD%, VLD% and FD within the SVC of eyes in the PATs might represent the effects of pathological amyloid and/or tau deposition in the SVC during the preclinical Alzheimer’s stage. If confirmed in larger longitudinal studies, OCTA evaluation of the SVC could be a biomarker for the early detection of Alzheimer’s.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

Table 1. OCTA in SVC.

 

Table 2. OCTA in DVC.