Laser Skin Resurfacing

Introduction
The cutaneous application of laser technology was launched in 1959 with the development of the 694-nm ruby laser by Maiman [1]. Over the next two decades, the argon laser, used to treat vascular lesions, and the carbon dioxide (CO₂) laser, used to vaporize epidermal and dermal lesions,became the focus of research and development [2]. Because these lasers yielded a high rate of hypertrophic scarring and pigmentary alteration due to excessive thermal injury to dermal tissue, their use in dermatology was limited. The theory of selective photothermolysis, developed by Anderson and Parrish in the early 1980s, literally transformed the field of cutaneous laser surgery by delivery of targeted thermal energy [3]. Laser surgery has since continued to be refined and is now considered an excellent, often primary, treatment choice for a wide variety of cutaneous applications.

The laser–tissue interaction first studied by Anderson and Parrish is based on three fundamental principles–wavelength, pulse duration, and fluence. The wavelength of emitted laser light is absorbed preferentially by a selected tissue target, or chromophore (e.g. hemoglobin, melanin, tattoo ink,water). Energy density (fluence) must be high enough to destroy the target within a set amount of time, also called pulse duration. The pulse duration ideally should be shorter than the target chromophore’s relaxation time (defined as the time required for the targeted site to cool to one half of its peak temperature immediately after laser irradiation). Optimization of these three parameters permits delivery of maximum energy to target structures with minimal collateral thermal damage.

The early argon and carbon dioxide lasers were continuous wave (CW) lasers, emitting a constant light beam with long tissue exposure durations, resulting in widespread thermal injury. Quasi-CW mode lasers, which shutter the CW beam into short segments, provided further refinement of this technology.As the thermal relaxation times of most chromophores are short, development of pulsed laser systems, which emit high-energy laser light in ultrashort pulse durations with relatively long time periods (0.1–1 s) between each pulse, marked a significant advancement in cutaneous laser surgery [4].

The use of lasers for aesthetic purposes has undergone exponential growth in the last decade to meet the demand for anti-aging technology. Currently, an abundance of laser and nonlaser technology exists for skin rejuvenation, scar revision, collagen tightening, and correction of cutaneous dyschromias. Treatment can be tailored to match the patient’s lifestyle and desired outcome (Table 7.1).

Table 7.1. Skin resurfacing laser and other systems. IPL intense pulsed light, RF radiofrequency, N/A not applicable       System types           Ablative   Nonablative       CO2 (10,600 nm) Erbium (2,940 nm)   Pulsed dye (585–595 nm) Nd:YAG (1,320 nm) Diode (1,450 nm) Er :Glass (1,540 nm) IPL (515–1,200 nm) RF (N/A)   Advantages   Best clinical outcomes Single procedure   No postoperative recovery Minimal risk of side effects   Disadvantages   Prolonged recovery Increased side effects   Subtle clinical effect Multiple sessions required