The introduction of laser surgery resurfacing has revolutionized advanced cosmetic surgery options for all skin types over the past 25 years.1-5 Laser resurfacing is divided into ablative and nonablative surgery. Ablative resurfacing refers to the destruction of the epidermis in an effort to improve texture, tone, and overall quality of the skin. Both the carbon dioxide (CO2) and erbium:yttrium-aluminum-garnet (Er:YAG) lasers have proven to be extremely effective in improving photoinduced rhytides, dyschromia, and scarring in patients with Fitzpatrick I–III skin.6 These ablative lasers have also proven to be effective in darker skin types but carry a greater risk of transient or permanent dyspigmentation.
Nonablative resurfacing refers to surgical treatment of the dermis while preserving the epidermis. A variety of lasers, including the pulsed dye lasers (PDL), Neodymium-yttrium-aluminum garnet (Nd:YAG) lasers, and the diode lasers, have been used to improve the skin tone of both fair and dark-skinned patients. In addition, intense pulsed light (IPL) and radio frequency (RF) devices have been used with varying success to rejuvenate facial skin. Herein, nonablative resurfacing techniques for darker pigmented individuals will be discussed. Preoperative, intraoperative, and postoperative considerations will be emphasized.
OVERVIEW OF LASER PRINCIPLES
Since the elucidation of the principles of selective photothermolysis in 1983,7 laser technology in ablative and nonablative resurfacing has significantly improved. Key terms in laser medicine are given in Table 8.1. Understanding of laser properties is essential to understanding the principle of selective photothermolysis.
TABLE 8.1Laser Terminology |Favorite Table|Download (.pdf) TABLE 8.1 Laser Terminology
|Chromophore ||The intended target of the laser light is called a chromophore. |
|Fluence ||The amount of energy that is delivered to a certain surface area is called fluence. It is typically measured in J/cm2. |
|Thermal relaxation ||The conduction of heat to the surrounding tissues |
|TRT ||The time it takes the chromophore to cool down to 50% of its peak temperature |
|Pulse duration ||The length of time the target chromophore is exposed to the laser light |
|Selective photothermolysis ||Using just the energy required to destroy the intended chromophore without causing damage to the surrounding tissue |
Laser light is unique in that it is monochromatic. The emitted single wavelength must be absorbed by a target to have an effect. Various chromophores, such as melanin, hemoglobin, and water, absorb light at different wavelengths. As the fluence increases, the amount of laser energy transmitted to the chromophore increases.
When the light energy is absorbed by the target, the chromophore converts the laser light energy to heat.7 The chromophore will be destroyed if enough heat is generated at a fast enough rate. Depending on the desired outcome, different rates of energy delivery can be chosen. This rate of energy delivery must be more rapid than the rate at ...