Optical coherence tomography angiography as a novel approach to contactless evaluation of sublingual microcirculation: A proof of principle study

Microcirculatory disorders are crucial in pathophysiology of organ dysfunction in critical illness. Evaluation of sublingual microcirculation is not routinely conducted in daily practice due to time-consuming analysis and susceptibility to artifacts. We investigated the suitability of optical coherence tomography angiography (OCTA) for contactless evaluation of sublingual microcirculation. Sublingual microcirculation was imaged in 10 healthy volunteers, using an OCTA device and an incident dark field (IDF) illumination microscopy (current gold standard). OCTA images were analyzed with regard to flow density and perfused vessel density (PVD(byOCTA)). IDF videos were analyzed following current recommendations. Flow density was automatically extracted from OCTA images (whole en face 48.9% [43.2; 54.5]; central ring 52.6% [43.6; 60.6]). PVD(byOCTA) did not differ from the PVD calculated from IDF videos (PVD(byOCTA) 18.6 mm/mm² [18.0; 21.7]) vs. PVD(byIDF) 21.0 mm/mm² [17.5; 22.9]; p = 0.430). Analysis according to Bland-Altman revealed a mean bias of 0.95 mm/mm² (95% Confidence interval −1.34 to 3.25) between PVD(byOCTA) and PVD(byIDF) with limits of agreement of −5.34 to 7.24 mm/mm². This study is the first to demonstrate the suitability of OCTA for evaluating sublingual microcirculation. Comparison of the perfused vessel density between methods showed a plausible level of agreement.