The histology of skin treated with a picosecond alexandrite laser and a fractional lens array

BACKGROUND AND OBJECTIVES: The treatment of acne scars and wrinkles with a picosecond Alexandrite laser was recently FDA cleared. In 2014 we presented our initial histologic findings with this device on in vivo and ex vivo skin. This current study expands on the 2014 pilot study with an investigation of different energy settings using histology and the confocal microscope to describe the changes observed in the skin. MATERIALS AND METHODS: We used a 755 nm picosecond Alexandrite laser with a fractional optic with three different energy settings to treat in vivo. After treatment, the patients and skin samples were also evaluated with a confocal microscope followed by biopsies which were evaluated histologically. RESULTS: Histology revealed unique intra-epidermal cavities. The number, density, and the size of these cavities were dependent on the melanin index and delivered energy when evaluated with histopathology and the confocal microscope. These localized zones of injury appear to form microscopic epidermal injury zones which are exfoliated over a 3-week period. CONCLUSIONS: These intra-epidermal cavities result from areas of laser-induced optical breakdown (LIOB). This injury is most consistent with a localized plasma formation in the epidermis initiated by the melanin absorption of the high energy picosecond light. It appears that treatments with this device and optic result in improvements in dyspigmentation and acne scars with new collagen, elastic tissue, and mucin. The production of this LIOB could directly stimulate an epidermal repair mechanism that results in these clinical findings. Lasers Surg. Med. 48:646-652, 2016. © 2016 Wiley Periodicals, Inc.