For the laser surgeon, the Er-YAG laser is an invaluable tool that delivers unsurpassed ablation efficiency, and with appropriate functionality (quasi long-pulse feature) provides sufficient tissue coagulation to remodel deep rhytids. As such, the 2940-nm wavelength is well suited for routine laser skin rejuvenation in full-field, fractional, and point-beam modes with additional benefits, including applicability to diverse skin types, short healing times, and a low likelihood of energy-related complications.
Despite alternative methods for skin rejuvenation, including nonablative fractional laser therapy, photorejuvenation, photodynamic therapy, medium and deep chemical peels, ablative fractional laser therapy, and other treatments, full-field (complete surface coverage) ablative laser therapy remains popular for patients seeking maximum improvement with a single treatment. Ablative laser skin resurfacing (LSR) wavelengths include 2790 nm (erbium:yttrium-scandium-gallium-garnet or Er-YSGG), 2940 nm (erbium:yttrium-aluminum-garnet or Er-YAG), and 10,600 nm (carbon dioxide or CO 2 ). Of these, the Er-YAG laser wavelength is an excellent choice for improvement of a variety of skin conditions and features of aging, including dyschromia, actinic photodamage, solar elastosis, acne and traumatic scarring, fine lines and mild to moderate rhytidosis, coarse skin texture, and skin laxity.
Similar therapeutic benefits, including skin tightening, are well established with the carbon dioxide and Er-YSGG wavelengths ; however, overall benefit, including rhytid effacement, skin tightening, and long-term improvement has long been considered by many physicians to be superior with the CO 2 wavelength. Even so, traditional multipass ablative full-field CO 2 LSR has declined in popularity owing to a number of factors, including higher risk of postresurfacing sequelae and complications, extended posttreatment recovery time, and increasing popularity and effectiveness of the alternative skin-resurfacing modalities enumerated previously. And when directly comparing full-field resurfacing lasers, it is the author’s opinion that the Er-YAG laser is an indispensible tool with an acceptably low risk-to-benefit ratio that, with appropriate functionality, enables physicians to effectively treat aging skin and other conditions in patients with a greater diversity of skin types.
The first Er-YAG laser was introduced commercially in 1997. In practice, the first Er-YAG skin-resurfacing lasers proved to be effective for soft tissue ablation but not for soft tissue coagulation. The initial excitement about the 2940-nm alternative wavelength diminished with the realization that the first-generation devices required multiple passes to ablate into the upper dermis and that on reaching this depth, significant bleeding caused difficulty with completion of treatments and also reduced the ablation efficiency of the device at that point during treatment. Second-generation Er-YAG lasers (circa 1999) avoided unchecked bleeding by adding a long-pulse or variable-pulse feature designed to provide significant soft tissue coagulation ability.
The flexibility to deliver Er-YAG laser energy for “pure” ablation or “pure” coagulation as well as a user-determined blend of ablation and coagulation to precise tissue depths led to recognition of these devices (those with long-pulse or variable-pulse modes) as extremely versatile. Full-field ablative Er-YAG LSR options that remain relevant more than a decade later (even with the interim development of many other useful treatment modalities) include superficial (partial epidermal), moderate depth (ablation into upper dermis), and deep skin peels (mid-papillary dermis or deeper) and combinations with other treatment modalities (eg, superficial peel and photorejuvenation).
The benefits of nonablative fractional laser treatment (including wavelengths of 1410, 1450, 1540, 1550, and more recently 1927 nm) profoundly influenced the approach to laser skin rejuvenation and also led to use of this novel type of energy delivery with the ablative laser wavelengths. Reduction of initial posttreatment recovery time (compared with traditional full-field LSR; dramatic for nonablative fractional resurfacing [NFR] and modest for ablative fractional resurfacing [AFR]), extension of these treatment modalities to additional skin types and conditions, widespread patient acceptance, and significant demand has legitimized this alternative approach.
Nonetheless, an area of current interest is the middle ground between pure AFR and pure full-field LSR, where the potential for very significant improvement, while preserving at least some of the benefits of AFR and of LSR, exists by combining these very different approaches to delivery of laser energy to the skin. The advantages of dual-wavelength (CO 2 and Er-YAG) LSR have been explored in detail in the past. By partial extension, a novel approach currently in use by the author and others involves concurrent dual-wavelength, dual-modality laser skin rejuvenation wherein CO 2 AFR deep dermal ablation immediately precedes or immediately follows full-field Er-YAG LSR.
Er-YAG laser tissue interaction
The Er-YAG laser wavelength has the highest absorption coefficient for water among the ablative laser wavelengths ( Fig. 1 ) with approximately 12 times and 5 times greater absorption in water versus CO 2 and Er-YSGG, respectively. During LSR, water serves as the primary tissue target wherein light energy is transduced into heat energy that is then quickly absorbed by the surrounding tissues, including collagen. The characteristic tissue interactions that define each of the ablative resurfacing lasers are related to their relative absorption by water but also several other factors. The continuum of responses to heating of biologic tissues includes hyperthermia, coagulation, carbonization, and vaporization and each of these may be observed during LSR. In general terms, higher water absorption is correlated with greater tissue ablation (vaporization), whereas lower water absorption is correlated with greater tissue coagulation.
