Abstract
Presentation Description :
As an extension of the central nervous system, retinal and choroidal vascular alterations have long been thought to be possible imaging markers of multiple sclerosis (MS) and Alzheimer's disease (AD). This talk will review the current status of optical coherence tomography angiography studies in patients with MS and AD by providing evidence in the literature to support the potential use of new metrics for exploring ocular vascular changes as biomarkers for disease progression.
Most studies reported significantly lower retinal vascular density (VD) and choroid thinning for patients with AD compared to controls. In contrast, increased VD was reported in the preclinical individuals: cognitively healthy participants with high genetic risk (parental history of AD or at least one ε4 allele of ApoE) or cerebral Aβ+ positive. The possible explanation for higher VD in the preclinical stage is more opening of microvessels due to increased blood flow secondary to an inflammatory reaction. Those microvessels are eventually damaged by continued inflammation and accumulation of Aβ with disease progression. The bidirectional changes of VD during the disease course indicate it might not be a sensitive biomarker. Similar inconsistent macular VD and choriocapillaris density of patients with MS were reported among different studies. These discrepancies could be due to differences in patient cohorts, equipment, techniques, and analytic methods. However, the other possibility could be that the retinal neuronal structural changes were not considered. The mild diffuse inflammation may cause both neuronal and vascular damage; meanwhile, VD alterations could be due to the decreased metabolic demand secondary to neurodegeneration. Hence, simultaneous analysis of the changes in both the retinal vascular and neural structure, such as volumetric vessel density (VVD) calculated as VD normalized by the corresponding tissue volume, may help better understand the interaction between these two critical components. Furthermore, retinal capillary function (RCF), considering VD and blood flow, may be more sensitive in detecting microvascular alterations. Future longitudinal large-sample studies of VVD and RCF on patients with MS and AD may enlighten the potential of using RCF and VVD as biomarkers to monitor disease progression.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.