## 4 Discussion
A longer follow-up seems to be necessary to monitor the long-term evolution of altered vascularization. This observation suggests that vascular normalization may be a gradual process that continues beyond the initial treatment phase. A longer follow-up is indeed necessary to monitor the long-term evolution of altered vascularization, as it could provide critical information about the durability of treatment effects and potential need for maintenance therapy. By enabling the visualization of these persistent vascular changes, LC-OCT offers clinicians a powerful tool for assessing treatment response, adjusting therapeutic strategies, and making informed decisions about the continuation or modification of systemic treatments. These vascular alterations might serve as a marker for severe psoriasis and need for systemic treatment when detectable in healthy skin. For further evaluation, a comparison between patients suffering from severe psoriasis compared to patients suffering from mild or moderate psoriasis receiving only topical treatment might be of great value in the future, including an analysis of clinically healthy skin. AI model analysis of previously segmented LC-OCT scans for the evaluation of vessels might be of interest in the evaluation of treatment response and continuation or discontinuation of therapy. Dilated vessels seem to persist longer than acanthosis and hyperkeratosis. The diminution of hypervascularization could be investigated as a marker for treatment response. AI-enhanced analysis might be of great help in objectively measuring the extent of increased vasculature. In our study, in contrast to the study by [PERSON], [PERSON] [22], the SP's location was not restricted to the patients' back, but different body regions were included without limitations. LC-OCT scans are feasible in various and diverse body parts. For evaluation, anatomical features and peculiarities like variation in the thickness of healthy epidermis and dermis must be considered for analysis. AI model segmentation and measurement of skin layers were carried out in complete 3D stacks, thus generating more reliable values. In the preceding study by [PERSON], [PERSON] [22], segmentation and measurements were only carried out in several vertical images per patient. In their study, 3D stack segmentation was only conducted in a few patients and not used for statistical analysis, thus not generating such a reliable mean. In our study, the exact measurement of the ET was initially not possible in 8 of 12 patients, and therefore, no analysis of the upper dermis was possible. This is due to excessive hyperkeratosis as well as acanthosis and the limited penetration depth of the LC-OCT. Similar findings have been reported by [PERSON], [PERSON] [22]. Visualization improved during therapy in concordance with reduction in the LPSI. Statistical analysis was performed using the highest measurable ET, although a higher thickness can be presumed. Therefore, the statistical significance of the reduction would not change when considering even higher initial values. The inability of LC-OCT to measure ET in 8 out of 12 patients at baseline due to excessive hyperkeratosis and acanthosis underscores a critical limitation of the technology in clinical and research applications. The high, nearly cellular resolution of the LC-OCT contrasts the limited penetration depth of the device. It has to be taken into account that it is already offering a greater penetration depth compared to RCM, which offers a similar resolution. This issue highlights the need for further refinement in LC-OCT's imaging capabilities to effectively penetrate and resolve highly keratinized or thickened epidermal layers. The challenge reduces the generalizability of findings, particularly in populations with conditions characterized by significant epidermal alterations.