High resolution imaging and quantification of the nailfold microvasculature using optical coherence tomography angiography (OCTA) and capillaroscopy: a preliminary study in healthy subjects

Analysis of microvascular pattern in diabetes mellitus condition using the nailfold capillaroscopy images

Diabetes is often considered a vascular disease due to its impact on blood vessels, it is a complex condition with various metabolic and autoimmune factors involved. One of the long term comorbidities of diabetes includes microvascular complications. The microvascular complications can be analyzed using the Nailfold capillaroscopy, a non-invasive technique that allows for the visualization and analysis of capillaries in the proximal nailfold area. Using advanced video capillaroscopy with high magnification, capillary images can be captured from and processed to analyze their morphology. The capillary images of normal group and diabetic group are acquired from 118 participants using nailfold capillaroscopy and the obtained images are preprocessed using image processing filters. The identification and segmentation of the capillaries are the challenges to be addressed in the processing of the images. Hence segmentation of capillaries is done using morphological operations, thresholding and convolutional neural networks. The performance of the filters and segmentation methods are evaluated using Mean Square Error (MSE), Peak signal to Noise Ratio (PSNR), Structural Similarity Index Measure (SSIM), Jaccard Index and Sorensen coefficient. By analyzing the morphological features namely the capillary diameter, density, distribution, presence of hemorrhage and the shape of the capillaries from both the groups, the capillary changes associated with diabetic condition were studied. It was found that the non diabetic participants considered in this study has capillary diameter in the range of 8-14 µm and the capillary density in the range of 10-30 capillaries per mm2 whereas the diabetic participants has capillary diameter greater than 30 µm and the capillary density is less than 10 capillaries per mm2. In addition to capillary density and diameter, the presence of hemorrhage, the orientation and distribution of the capillaries are also considered to differentiate the diabetic group from the non diabetic group. The classification of the participants are validated with the clinical history of the participants.

Peripheral and ocular microvascular alterations in systemic sclerosis: observations from capillaroscopic assessments, perfusion peripheral analysis, and optical coherence tomography angiography

To investigate the correlations between finger microvascular morphology and function in patients with systemic sclerosis (SSc) and the status of ocular microcirculation, as detected by nailfold videocapillaroscopy (NVC), laser speckle contrast analysis (LASCA), and optical coherence tomography angiography (OCTA). The enrollment included 32 SSc patients, classified according to the 2013 ACR/EULAR criteria, and 27 sex- and age-matched healthy controls. The participants underwent comprehensive rheumatological and ophthalmological examinations, as well as NVC, LASCA, and OCTA analysis on the same day at a single center from March to October 2022. SSc patients receiving intravenous prostanoids cycles were assessed at least 1 month after infusion. Statistical analysis was conducted using Stata® 15.1. Significant direct correlations were observed between the mean capillary number (at NVC) and the mean perfusion of fingers (at LASCA) with the retinal and choroidal perfusion (at OCTA) (all p < 0.05). In addition, a significantly reduced retinal and choroidal perfusion was detected in SSc patients vs controls (all p < 0.05). Interestingly, diffuse cutaneous SSc (dcSSc) patients exhibited a lower choroidal perfusion (p = 0.03) but an increased choroidal thickness (CT) than limited cutaneous SSc patients (p < 0.001). CT was increased also in patients with positive Scl70 antibodies and with a history of digital ulcers directly correlating with disease duration (r = 0.67, p = 0.001). Finally, the combination of LASCA and OCTA parameters showed a significant discrimination capacity between SSc patients and controls, with an area under the curve of 0.80 [95% CI (0.74, 0.87)]. Peripheral microvascular damage is correlated with impaired ocular microcirculation in SSc. The increased choroidal thickness observed in dcSSc may be related to local sub-endothelial extracellular matrix deposition. The combined analysis of choroidal and fingertip perfusion offers preliminary insights that may complement traditional diagnostic methods for SSc.