Utilizing the principles of selective photothermolysis, ablative removal of skin in a precisely controlled fashion with resultant minimal surrounding thermal damage is achieved. The depth of tissue penetration is dependent on selective absorption of water. Immediate tissue effects are dependent on the spot size and power utilized as well as the speed of treatment administration. The time of laser–tissue interaction is the critical factor for residual thermal damage. Epidermal obliteration and(or partial ablation or coagulation of the upper dermis is the endpoint. Re-epithelialization results from the migration of cells that arise from surrounding follicular adnexae. Normal compact collagen and elastic fibers replace the amorphous elastotic dermal components, and normal, well-organized epithelial cells replace the disorganized photodamaged epidermis. Collagen remodeling is noted both intraoperatively via thermal shrinkage and contraction and postoperatively within the remodeling phase of wound healing.
Carbon Dioxide Laser (CO2 Resurfacing)
Continuous wave (10,600 nm), super-pulsed, and scanned CO2 lasers are utilized for resurfacing. A relatively bloodless surgery with reduced swelling is achieved via the photocoagulative effect on blood vessels and lymphatics. The risk of scarring, unpredictable level of thermal damage, and delayed healing of the continuous wave laser limit its clinical use. The scanned and pulsed CO2 lasers deliver high peak fluences in less than 0.001 seconds to achieve tissue vaporization of 20 to 30 μm per pass. Approximately 40 to 120 μm of residual thermal damage is noted per pass (Fig. 7.1).
Figure 7.1 (A)
A 58-year-old woman with extensive actinic damage.
Figure 7.1 (B)
A marked reduction in rhytides and dyspigmentation is noted 2 months after full-face carbon dioxide resurfacing
Erbium:Yttrium-Aluminum Garnet Laser (Er:YAG)
A laser of wavelength 2,490 nm is utilized for more superficial resurfacing. It is 16× more selectively absorbed by water. It achieves tissue vaporization of 1 to 5 μm per pass. It results in a narrower zone of residual thermal damage (5–30 μm). As a zone of thermal damage of 50 μm or greater is required for photocoagulation, Er:YAG treatment results in a slightly bloody surgical field. The thermal damage is also insufficient to produce immediate collagen contraction. Long-term collagen remodeling is limited (Fig. 7.2).
Figure 7.2 (A)
A 45-year-old woman with facial photoaging and mild acne scarring.
Figure 7.2 (B)
Improvement of photoaging 3 weeks after full-face erbium treatment
Ablative lasers have been utilized as a cutting tool and vaporizing tool to treat epidermal and superficial dermal lesions.