The Value of OCT and OCTA as Potential Biomarkers for Preclinical Alzheimer’s Disease: A Review Study

Abstract

Preclinical Alzheimer’s disease (AD) includes cognitively healthy subjects with at least one positive biomarker: reduction in cerebrospinal fluid Aβ42 or visualization of cerebral amyloidosis by positron emission tomography imaging. The use of these biomarkers is expensive, invasive, and not always possible. It has been shown that the retinal changes measured by optical coherence tomography (OCT) and OCT-angiography (OCTA) could be biomarkers of AD. Diagnosis in early stages before irreversible AD neurological damage takes place is important for the development of new therapeutic interventions. In this review, we summarize the findings of different published studies using OCT and OCTA in participants with preclinical AD. To date, there have been few studies on this topic and they are methodologically very dissimilar. Moreover, these include only two longitudinal studies. For these reasons, it would be interesting to unify the methodology, make the inclusion criteria more rigorous, and conduct longer longitudinal studies to assess the evolution of these subjects. If the results were consistent across repeated studies with the same methodology, this could provide us with insight into the value of the retinal changes observed by OCT/OCTA as potential reliable, cost-effective, and noninvasive biomarkers of preclinical AD.

Retinal microvasculature and imaging markers of brain frailty in normal aging adults

“…Neuropsychological assessments such as the MoCA is a fundamental approach that is used to assess the cognition in individuals. The association between OCTA variables and the MoCA has been suggested to be useful in the clinical evaluation and monitoring of patients with cognitive dysfunction ( Zhang et al, 2020 ; López-Cuenca et al, 2021 ). Our current report showed that the MoCA scores significantly correlated with SVC changes in aging individuals, which are congruent with previous reports.…”

Neuroimaging modalities in the detection of Alzheimer's disease-associated biomarkers

“…In addition, nuclear imaging modalities have some disadvantages, such as high cost, poor resolution, long testing times, and unavoidable exposure to radioactivity (Xu et al ., 2016 ). Optical imaging modalities, particularly NIRF imaging, may provide a non-invasive in vivo method to visualize the real-time status of the AD brains more accurately at the biomolecular level (Liu et al ., 2021b ; López-Cuenca et al ., 2021 ). Importantly, small molecule NIR probes are used to detect Tau protein, β-amyloid, and other biomarkers (Rai et al ., 2022 ).…”

Ratiometric analysis of in vivo optical coherence tomography retinal layer thicknesses for detection of changes in Alzheimer's disease

“…A systematic review of 71 studies such as this found that while AD patients often exhibit retinal thinning on OCT retinal scans, the literature lacks sufficient evidence on the specific areas of the retina that undergo changes [15]. Another review of 64 studies focusing on biomarker identification using OCT in patients with AD concluded that a very limited number of studies analyze patients with preclinical AD or are longitudinal, arguing that conducting studies following the evolution of preclinical AD patients would be of great value [16]. These identified gaps in the literature motivate a longitudinal study of retinal layer changes in AD patients.…”