The Utilization of Optical Coherence Tomography in the Assessment of Melasma Activity and Differential Diagnosis

Melasma represents a prevalent facial hyperpigmentation disorder that predominantly affects Asian females. This study aims to assess the applicability of Optical Coherence Tomography (OCT) in the cases of melasma, Hori's nevus, and freckles and to summarize the features of OCT images.

This single-center, evaluator-blinded, observational study was carried out at the Department of Dermatology, Peking Union Medical College Hospital from October 2024 to June 2025. All participants underwent noninvasive dermoscopy, reflectance confocal microscopy, and OCT examinations of lesional and perilesional areas.

47 patients with melasma, 6 patients with Hori's nevus, and 13 patients with freckles were included. 18 patients with melasma (38.3%) were categorized into the active stage, whereas 29 patients with melasma (61.7%) were classified into the stable stage. A disruption of the basement membrane zone exceeding 50% and blood vessel dilation were more frequently observed in the active stage (p < 0.05). In the context of differential diagnosis, a disruption of the basement membrane zone exceeding 50% can be regarded as a differentiating factor among melasma, Hori's nevus, and freckles (p < 0.05).

OCT can unveil the characteristic features of different melasma stages and offer crucial information for melasma staging and differential diagnosis.