## 4 Discussion
To address this, future efforts should focus on enhancing the imaging resolution depth, developing adaptive algorithms for image interpretation in hyperkeratotic tissues, and exploring adjunctive methods to preprocess or optimize tissue visualization. Another solution might be to add a second imaging tool with a greater penetration depth like OCT to provide deeper insights. Acknowledging and tackling these limitations is essential to expand the applicability of LC-OCT in diverse dermatological conditions. The technical improvementsof the LC-OCT, leading to a bigger penetration depth in the future, would offer a great advantage in the examination of PP. In one patient, the SP was located in the prepetellar region. This is an area with physiologically higher epidermal thickness, especially in psoriatic lesions in this location [41]. The patient showed clinical improvement under therapy (V0: PASI = 32.2, LPSI = 10; V2: PASI = 8.7, LSPI = 2), but due to the SP's location, the dermis remained non-measurable during the study period. Other regions did not show such limitations among the study population. Limitations of this study are the small number of participants, the single-center design, the relatively short study duration, and the lack of subgroup analysis. Follow-up studies with bigger study populations will be needed in the future. This would also offer the possibility of subgroup analysis, e.g., concerning mild and severe psoriasis or different therapeutic treatment modalities. Adding a multi-center design would offer further examination of comparability between different examiners. The control period of 3-4 months was calculated regarding the time needed to reach a significant clinical improvement, which was remarkable most of the time in this time period. We now note that psoriatic changes in the epidermis and dermis seem to be observable longer than clinical alterations (judged by the application of the LPSI). This is a novel insight and could therefore not be known before the initiation of the study. The persistence of vascular changes and also inflammatory patterns during the chosen study period of only three months should give rise to longer examination periods in the future. Longer control periods seem to be necessary in future studies and will be taken into account for planning future studies. An examination of the SP and CoA was carried out with clinical scores and LC-OCT; we did not compare different non-invasive imaging modalities. This is something that may be necessary in future investigations since other imaging modalities, like dynamic optical coherence tomography, can offer a higher visualization depth compared to that of LC-OCT. A comparison would also offer objective verification of the reliability of the findings in each non-invasive imaging tool. Our study population consisted of severe cases of psoriasis in need of systemic treatment with biologics. The examination of mild to moderate psoriasis under different treatment modalities should be carried out in future research to allow for the comparison of inflammatory patterns. To date, there is no standard concerning the decision of continuation or termination of therapy with biological agents. Long-term follow-up with non-invasive imaging tools might offer the detection of possible prediction markers for long-term remission.