the laser, measured in watts, takes all three of the above variables into account and is commonly used to describe the energy delivered by the laser.

In addition to the physics of the laser, individual patient characteristics must also be considered including skin type, possible wound healing or scarring history, the patient’s age, the thickness of the patient’s skin, and the region to be treated. The most commonly used skin type classification system is the Fitzpatrick classification, which is described as follows:

Class 1: Very fair skin, never tans, always burns Class 2: Fair skin, mildly tans, nearly always burns Class 3: Medium skin tone, tans, sometimes burns Class 4: Medium-dark skin, tans, still may occasio-

nally burn

Class 5: Dark skin, tans intensely, rarely burns Class 6: Darkest skin, tans intensely, never burns

Patients with skin class 4–6, are at high risk for dyschromia post-resurfacing and are thus rarely candidates for laser facial resurfacing. Any possible wound healing concerns should be assessed as should the thickness of the patient’s skin. Finally, the regions of skin that are to be treated must also be considered. For example, the thin skin of the eyelids will require less energy than the thicker and appendage-rich skin of the cheek regions. This last consideration will influence the laser settings used as well as the number of passes of the laser. The energy of the first pass of the laser is nearly completely absorbed by epidermal water; however, once this layer has been removed, passes of the laser into dermal layers, which have less water content, results in greater heating of surrounding tissues leading to more injury with each pass.

14.2 Technique

14.2.1 Preoperative Preparation

Resurfacing of patients with darker skin types leads to a much more unpredictable result and is not routinely performed. All patients who desire laser resurfacing of the face should be informed that the procedure is one that is capable of producing unpredictable results, especially in terms of final results, recovery time, and complications [8]. Pretreatment of the skin is commonly recommended and may include sun avoidance,

hydroquinone, isotretinoin, and glycolic acids. Sun avoidance is particularly important due to the theoretical risk of sun-induced melanocyte activation, which may result in unpredictable post-procedure pigmentary changes [8].

Prophylactic antivirals should be initiated in all patients and is routinely started 2 days prior to the procedure and continues for 14 days or until reepithelialization is complete. The risk of viral eruption following resurfacing is approximately 5% [7, 9–11]. Prophylactic antibiotic use is much more controversial and variable [12]. Many surgeons use preand post-procedure antibiotics routinely, whereas others use them only on a case-by-case basis. Many surgeons will also provide patients with prophylactic antifungal medications.

Preoperative photographs can be a helpful tool to help patients remember their preoperative appearance and can be used to document the patient’s progress (Figs. 14.1 and 14.2). Cosmetic units may be marked in the preoperative holding area when the patient is in the upright position. This helps ensure that no error in marking will occur, as may happen when the patient is in the supine position due to skin movement. In addition, marking prior to the procedure helps avoid the temptation of marking intraoperatively, which may result in permanent tattooing if ablated skin is exposed to ink.

14.2.2 Carbon Dioxide Laser

Although initially invented in the 1960s, use of the carbon dioxide laser was limited due to long pulse durations, which led to unwanted thermal diffusion and subsequent scarring [1]. The development of lasers, capable of much shorter pulse durations (less than 1 ms), led to much more controlled and reproducible results. Now, the carbon dioxide laser is typically used for rhytids in the shallowto medium-depth range and is particularly useful for treating solar and actinic damage. Tissue ablation depth is approximately 50–100 Pm and the thermal diffusion injury range is 35–50 Pm. Settings used for the carbon dioxide laser vary; however, standard settings are density of 4–5 with an energy delivery of 80–90 mJ that corresponds to a power of 45–60 W [8].

The laser is passed over the areas of the face to be treated with care taken to the different skin depths in different regions of the face. The level of ablation that is

required is dependent on the skin thickness, degree of rhytidosis, and the patient’s age. This latter point is important to remember, because aging is associated with thinning of the skin. The depth of ablation can be determined by the color of the underlying ablated tissue. A pink color indicates the upper papillary dermis, whereas a gray color indicates the upper reticular dermis, and a chamois appearance with pinpoint bleeding

indicates the mid-reticular dermis. Secondary passes over regions are usually performed with a lower energy, for example, 60–70 mJ, with a density of 4. Second passes are used for deeper wrinkles that require more than one pass to reach the base of the rhytid. A moist saline-soaked gauze sponge can be used to remove ablated tissue between each pass of the laser. Blending of the treated skin with non-treated regions is important,

because nearly all patients will develop some degree of hypopigmentation postoperatively [8].

14.2.3 Erbium Laser

The erbium laser has a wavelength of 2,940 nm, which corresponds to a point on the water absorption curve that is approximately ten times greater than that seen with the wavelength of the carbon dioxide laser [1]. The clinical relevance of this difference is a laser with a much greater safety margin secondary to less tissue injury to the surrounding tissues. This leads to a decreased improvement in rhytids compared to the carbon dioxide laser; however, it is also associated with less postoperative erythema, shorter recovery time, less scarring, and decreased risk of pigmentary changes. Greater thermal injury can be achieved by increasing the duration of the pulse.

The procedure of resurfacing with the erbium laser is similar to that described with the carbon dioxide laser. Again, the depth of ablation must be carefully monitored to avoid too deep ablative treatment and scarring. The classic color changes described above for the carbon dioxide laser are not seen. Instead, pinpoint bleeding should be used as an indicator that the depth of ablation is in the papillary dermis. Ablative debris must be removed after each pass. However, the erbium laser is not associated with thermal stacking allowing for overlapping of passes.

Due to the decreased thermal diffusion, the erbium laser has less tissue penetration than the carbon dioxide laser. Utley demonstrated that the erbium laser penetrated 20 Pm with the first pass, whereas the carbon dioxide laser had a penetration depth of 62.5 Pm [13]. These differences allow anesthesia for resurfacing with the erbium laser to be performed with local or even topical anesthesia if the level to be resurfaced is superficial. Otherwise, for deeper peels, local