Laser skin resurfacing using a frequency doubled Nd : YAG laser after topical application of an exogenous chromophore

Background and Objectives: Although laser skin resurfacing performed with C O2 or Er:YAG lasers is efficient, side effects such as prolonged postoperat ive erythema, delayed healing, scarring, and pigmentation, have been report ed. These side effects are due to skin characteristics but also to variatio ns of the thermal effects associated with laser skin resurfacing. The study aimed to evaluate a new laser resurfacing method based on a previous topic al application of an exogenous chromophore in order to have reproducible th ermal effects. Materials and Methods: Exogenous chromophore consisted in carbon dispersed and mixed with film-forming polymers and water. The resultant solution was applied to the skin surface using an airbrush. Experimental evaluation was performed in vivo on hairless rat skin using the following parameters (532 nm, 2.7 W, 1 mm, 50-200 ms, 17.2-68.8 J/cm(2), single pass). Skin biopsies were taken to evaluate histological changes and to quantify epidermis ablat ion and dermal coagulation depth. Wound healing was followed up during 10 d ays. Results: Total epidermis ablation was achieved with all pulse durations use d. Dermal coagulation depth increased as a function of exposure time. Scar formation was correlated with dermal coagulation depth. Conclusion: The concept of applying a carbon-based solution onto skin in or der to obtain laser light conversion into heat followed by heat transfer to the tissue is valid for laser skin resurfacing. By selecting exposure time , the thermal effects are predictable and dermal coagulation depth can be e ither that observed with a Er:YAG; laser or that obtained with a CO2 laser. Moreover, frequency doubled Nd:YAG laser, already used in dermatology for angiodysplasias treatment, could be easily used for resurfacing of periorbi tal or perioral zones. Lasers Surg. Med. 25:43-50, 1999. (C) 1999 Wiley-Lis s, Inc.