Abstract
Purpose :
Individuals with Alzheimer’s Disease (AD) exhibit decreased retinal blood flow and vessel density. However, it is not known whether these changes are also present in individuals with amnesic type mild cognitive impairment (aMCI), an enriched pre-AD population with a higher risk for converting to AD. We performed a prospective case-control clinical study to investigate whether optical coherence tomography angiography (OCTA) parameters in the macula and disc may provide useful biomarkers in those with aMCI and early AD (eAD).
Methods :
We recruited participants with aMCI/eDAT (n=16) that were 1:1 age-, gender-, and race-matched to cognitively normal controls (n=16). We analyzed OCTA images of the parafoveal superficial capillary plexus (SCP) and two vascular layers in the peripapillary region, the radial peripapillary capillary (RPC) and superficial vascular complex (SVC). Outcome vascular and structural parameters included vessel density (VD), vessel length density (VLD)—a measure of VD that removes the disproportionate influence of large vessels, adjusted flow index (AFI) and retinal nerve fiber layer (RNFL) thickness. We compared these parameters between the two groups and examined the correlation between the OCTA parameters and cognitive performance on the Montreal Cognitive Assessment (MoCA) test.
Results :
Cognitively impaired participants demonstrated statistically significant decrease in parafoveal SCP VD (40.67 ± 5.23, p=0.028) and AFI (0.376 ± 0.041, p=0.047) as compared to controls (SCP VD 44.50 ± 4.11, AFI 0.407 ± 0.037). We did not find a statistically significant difference in peripapillary parameters or RNFL thickness between the two groups. However, we did find a statistically significant positive correlation between MoCA scores for the entire study cohort and the parafoveal SCP VD (R=0.361, P=0.043) as well as the peripapillary RPC VLD (R=0.463, P=0.010).
Conclusions :
OCTA shows significant decline in the parafoveal flow and VD in individuals with aMCI/eDAT, suggesting these parameters could have potential utility as early disease biomarkers. In contrast, the presence of larger vascular channels in the peripapillary region may have obscured subtle capillary changes in that region. Overall, the correlation between vascular OCTA parameters and cognitive performance provides support for additional studies in this population using OCTA.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.