Histologic Effects of the High-Energy Pulsed CO2 Laser on Photoaged Facial Skin

To delineate the histologic effects of laser resurfacing at photoaged skin, a protocol was designed to biopsy laser test sites in conjunction with adjacent actinically damaged skin at the time of rhytidectomy. Five patients with photodamaged skin underwent resurfacing of the preauricular region to examine the effect of increasing pulse energy and increasing number of passes on depth of dermal penetration. Histologic examination of these specimens showed that the depth of laser injury was dose-dependent. Increasing pulse energy created a deeper wound, and increasing the number of passes similarly produced a larger band of necrosis. Ten patients with photodamaged skin underwent resurfacing of the preauricular region 15 days to 6 months prior to undergoing a rhytidectomy. A comparison of the laser-resurfaced test spot with the adjacent untreated photodamaged skin demonstrated consistent histologic changes to both epidermis and dermis in all specimens examined. Following laser resurfacing, epidermal atrophy and atypia were eliminated, and all specimens exhibited a regeneration of epithelium that was normal in its morphology. Melanocytic hypertrophy and hyperplasia were corrected following treatment, although density and function of epidermal melanocytes appeared normal. All specimens exhibited a substantial amount of neocollagen formation involving both the superficial and middermis following resurfacing. In association with new collagen development within the dermis, there was noted to be a similar degree of proliferation of elastic fibers, as well as a diminution of glycosaminoglycans, which are typically present in actinically damaged elastotic dermis. To determine the effect of laser resurfacing on-black skin, laser test spots were placed in the postauricular region of three black patients. Biopsy of these test sites showed that the histologic effects of laser resurfacing were similar to those observed in Caucasian patients, with complete repopulation of epidermal melanocytes in specimens biopsied 3 months following resurfacing. The histologic effects of laser resurfacing are microscopically similar to those of phenol peeling in terms of the amelioration of photodamage. The distinction between these two treatment methods lies in their apparent effect on epidermal melanocytes, which appear to function normally following laser resurfacing.