Deep segmentation of OCTA for evaluation and association of changes of retinal microvasculature with Alzheimer's disease and mild cognitive impairment

BackgroundOptical coherence tomography angiography (OCTA) enables fast and non-invasive high-resolution imaging of retinal microvasculature and is suggested as a potential tool in the early detection of retinal microvascular changes in Alzheimer's Disease (AD). We developed a standardised OCTA analysis framework and compared their extracted parameters among controls and AD/mild cognitive impairment (MCI) in a cross-section study. MethodsWe defined and extracted geometrical parameters of retinal microvasculature at different retinal layers and in the foveal avascular zone (FAZ) from segmented OCTA images obtained using well-validated state-of-the-art deep learning models. We studied these parameters in 158 subjects (62 healthy control, 55 AD and 41 MCI) using logistic regression to determine their potential in predicting the status of our subjects. ResultsIn the AD group, there was a significant decrease in vessel area and length densities in the inner vascular complexes (IVC) compared with controls. The number of vascular bifurcations in AD is also significantly lower than that of healthy people. The MCI group demonstrated a decrease in vascular area, length densities, vascular fractal dimension and the number of bifurcations in both the superficial vascular complexes (SVC) and the IVC compared with controls. A larger vascular tortuosity in the IVC, and a larger roundness of FAZ in the SVC, can also be observed in MCI compared with controls. ConclusionOur study demonstrates the applicability of OCTA for the diagnosis of AD and MCI, and provides a standard tool for future clinical service and research. Biomarkers from retinal OCTA images can provide useful information for clinical decision-making and diagnosis of AD and MCI.

Automated summary

This study developed a standardized OCTA analysis framework for retinal microvascular assessment and compared the parameters extracted from OCTA images between controls, Alzheimer’s Disease (AD), and mild cognitive impairment (MCI) groups. The results showed significant reductions in vessel area, length densities, and bifurcation numbers in AD group compared to controls. The MCI group demonstrated decreases in vascular parameters, fractal dimension, and bifurcation numbers in both superficial and inner vascular complexes, as well as increased vascular tortuosity and roundness of foveal avascular zone (FAZ). The study suggests that OCTA can be a useful tool for the diagnosis of AD and MCI.