Histopathological Changes After Experimental Skin Resurfacing Using an Improved Fractional High-Power 1064-nm Q-Switched Nd:YAG Laser

Background: Several studies confirm microscopic changes in the cutaneous architecture following various rejuvenation techniques using non-ablative lasers. Objective: To investigate the histological changes that occur after the application of an improved high-power 1064-nm fractional Q-switched Nd:YAG laser, using different focusing tips. Material and Methods: Experimental skin resurfacing of the retroauricular area in 15 female volunteers, in three treatment sessions of one pass each, using the Clear Lift laser (Alma Lasers, Israel) and five different focusing tips. Biopsies were taken before and immediately after the first treatment session, one month after the first session, and one month after the third session. A total of 60 microscopic images were evaluated at a micrometric scale. Results: The five tips used caused characteristic and similar histological changes in both the dermis and the epidermis. The signs of thermal damage and the formation of new collagen were observed at different depths, in accordance with the focal length of each tip. Neo-formation of collagen with the increase, reorganization and compaction of fibers began one month after the first treatment session, and was blindly confirmed, with all the tips used, one month after the third treatment session. Conclusion: The skin takes on a new conformation, with histological signs of skin rejuvenation, concordant with previous clinical observations.