Videomicroscopic and histopathological investigation of intense pulsed light therapy for solar lentigines

A noncoherent, broadband, intense pulsed light source has been effective for symptoms of photoaging skin as a nonablative method. The purpose of this study was to investigate the mechanism of efficacy of intense pulsed light for solar lentigines, a symptom of photoaging skin, with videomicroscopy and histopathology. Skin lesions of patients with solar lentigines who received one treatment of intense pulsed light were examined. Sixteen of 20 patients showed tiny crusts clinically. These tiny crusts were confirmed to be micro-crust formation after epidermal injury with sequential observation using videomicroscope and histopathology. Drop-off of micro-crusts with ample melanin pigments lead to clinical improvement of skin lesions. Intense pulsed light with absorption spectrum for melanin induced injury of melanin-containing epidermal cells via photothermal effects, suggesting that intense pulsed light may be a new modality for solar lentigines.