Modulation of Melanocyte in Melasma Patients After Picosecond Laser Treatment

Melasma is a therapeutically challenging hyperpigmented skin condition. Currently, there is a lack of in vivo observation regarding changes in melanin and dendritic melanocytes after laser treatment.

To investigate alterations in melanin and melanocytes in melasma before and after laser treatment using optical coherence tomography (OCT).

Eight female melasma patients were enrolled in Taiwan. Based on the baseline OCT scans, the patients were categorized into either epidermal-type or mixed-type melasma and were assigned different treatment protocols accordingly. Sequential OCT images were collected from melasma lesions and normal skin at baseline, Week 4 and Week 8.

After 8 weeks of laser treatment, the mean Melasma Area Severity Index (MASI) score improved from 10.92 to 6.30. Results from OCT showed no significant changes in the normalized density, area, or intensity of melanin in both lesional and normal skin. At baseline, the mean length of dendritic melanocytes in the affected skin was 15% longer than those in normal skin; at Week 8, the mean length of lesional dendritic melanocytes became the same as those in normal skin. Additionally, the mean width of dendritic melanocytes decreased from being 4% wider to only 2% wider than those in normal skin.

After 8 weeks of treatment, an improvement of MASI score was noted, mainly attributable to a reduction in lesional area. OCT showed no notable change regarding melanin, but a decrease in length and width of dendritic melanocytes was noted in the lesional skin of melasma patients.