Dynamic optical coherence tomography unveils subclinical, vascular differences across actinic keratosis grades I–III.

Actinic keratosis (AK) classification relies on clinical characteristics limited to the skin's surface. Incorporating sub‐surface evaluation may improve the link between clinical classification and the underlying pathology. We aimed to apply dynamic optical coherence tomography (D‐OCT) to characterize microvessels in AK I‐III and photodamaged (PD) skin, thereby exploring its utility in enhancing clinical and dermatoscopic AK evaluation. This explorative study assessed AK I‐III and PD on face or scalp. AK were graded according to the Olsen scheme before assessment with dermatoscopy and D‐OCT. On D‐OCT, vessel shapes, −pattern and ‐direction were qualitatively evaluated at predefined depths, while density and diameter were quantified. D‐OCT's ability to differentiate between AK grades was compared with dermatoscopy. Forty‐seven patients with AK I‐III (n = 207) and PD (n = 87) were included. Qualitative D‐OCT evaluation revealed vascular differences between AK grades and PD, particularly at a depth of 300 μm. The arrangement of vessel shapes around follicles differentiated AK II from PD (OR = 4.75, p < 0.001). Vessel patterns varied among AK grades and PD, showing structured patterns in AK I and PD, non‐specific in AK II (OR = 2.16,p = 0.03) and mottled in AK III (OR = 29.94, p < 0.001). Vessel direction changed in AK II‐III, with central vessel accentuation and radiating vessels appearing most frequently in AK III. Quantified vessel density was higher in AK I‐II than PD (p ≤ 0.025), whereas diameter remained constant. D‐OCT combined with dermatoscopy enabled precise differentiation of AK III versus AK I (AUC = 0.908) and II (AUC = 0.833). The qualitative and quantitative evaluation of vessels on D‐OCT consistently showed increased vascularization and vessel disorganization in AK lesions of higher grades. [ABSTRACT FROM AUTHOR]