HISTOLOGIC EFFECTS OF THE HIGH-ENERGY PULSED CO2-LASER ON PHOTOAGED FACIAL SKIN

To delineate the histologic effects of laser resurfacing of photoaged skin, a protocol was designed to biopsy laser test sites in conjunctio n with adjacent actinically damaged skin at the time of rhytidectomy. Five patients with photodamaged skin underwent resurfacing of the prea uricular region to examine the effect of increasing pulse energy and i ncreasing number of passes on depth of dermal penetration. Histologic examination of these specimens showed that the depth of laser injury w as dose-dependent. Increasing pulse energy created a deeper wound, and increasing the number of passes similarly produced a larger band of n ecrosis. Ten patients with photodamaged skill underwent resurfacing of the preauricular region 15 days to 6 months prior to undergoing a rhy tidectomy. A comparison of the laser-resurfaced test spot with the adj acent untreated photodamaged skin demonstrated consistent histologic c hanges to both epidermis and dermis in all specimens examined. Followi ng laser resurfacing, epidermal atrophy and atypia were eliminated, an d all specimens exhibited a regeneration of epithelium that was normal in its morphology. Melanocytic hypertrophy and hyperplasia were corre cted following treatment, although density and function of epidermal m elanocytes appeared normal. All spec imens exhibited a substantial amo unt of neocollagen formation involving both the superficial and midder mis following resurfacing. In association with ne iv collagen developm ent within tile dermis, there was noted to be a similar degree of prol iferation of elastic fibers, as well as a diminution of glycosaminogly cans, which are typically present in actinically damaged elastotic der mis. To determine the effect of laser resurfacing on black skin, laser test spots were placed in the postauricular region of three black pat ients. Biopsy of these test sites showed that the histologic effects o f laser resurfacing were similar to those observed in Caucasian patien ts, with complete repopulation of epidermal melanocytes in specimens b iopsied 3 months following resurfacing. The histologic effects of lase r resurfacing are microscopically similar to those of phenol peeling i n terms of the amelioration of photodamage. The distinction between th ese two treatment methods lies in their apparent effect on epidermal m elanocytes, which appear Is function normally following laser resurfac ing.