Erbium:Yttrium-Aluminum-Garnet Laser

Because of the potential morbidity associated with the CO₂ laser, efforts in the mid-1990s were directed at developing alternative resurfacing modalities. The short-pulsed erbium:yttriumaluminum- garnet (Er:YAG) laser was developed in an attempt to replicate the results of the CO₂ laser while minimizing the side-effect profile. The emitted wavelength of 2,900 nm is absorbed 12–18 times more efficiently by superficial cutaneous tissues, and approximately 2–5 µm of ablation occurs per pass with equally narrow zones of thermal necrosis [20].Clinically, this translates into a shorter postoperative healing time with much less posttreatment erythema and risk of hyperpigmentation than CO₂ lasers. However, immediate collagen contraction is only about 1–4%, and long-term collagen remodeling ranges from 0–14% [5]. Multiple passes with this laser are necessary to ablate to a similar depth as one pass of the CO₂ laser, and because the Er:YAG effects are photomechanical instead of photothermal (like the CO₂), intraoperative hemostasis is difficult to achieve [5, 21]. Therefore, the short-pulsed Er:YAG laser is limited in its utility for moderate-to-severe acne scars and photo-induced rhytids (Fig. 7.2).

Several studies have documented the effectiveness of the Er:YAG laser in the treatment of mild-to-moderate rhytids, photodamage, and atrophic scars, with the use of multiple passes, high fluences, and/or multiple sessions yielding improved clinical outcomes [22, 23, 24, 25]. The Er:YAG laser has also proven a good option for treatment of patients with darker skin types due to its lower risk of pigmentary alteration [26] and has even been used to treat melasma [27].

To address the limitations of short-pulsed systems, novel modulated systems have been developed to allow deeper zones of thermal damage and a greater level of hemostasis. Hybrid Er:YAG/CO₂ laser systems (e.g., Derma-K, Lumenis, Santa Clara, CA, USA) are capable of delivering both CO₂ energy for coagulation and Er:YAG energy for fine tissue ablation.The dual mode Er:YAG (e.g., Contour, Sciton, Palo Alto, CA, USA) combines short pulses (for ablation) with longer pulses (for coagulation). The variable- pulsed Er:YAG (CO₃, Cynosure, Chelmsford, MA, USA) system has a range of pulse durations from 500 µs to 10 ms, with the longer pulses effecting coagulation and thermal injury similar to the CO₂ laser [28]. As a group, these lasers have been shown to produce deeper tissue vaporization, greater control of hemostasis, and collagen contraction. This translates into greater clinical improvement in mild-to-moderate acne scars and photodamage than their short-pulsed predecessors and thus represent a good compromise between CO₂ and earlier generation Er:YAG lasers [29, 30, 31, 32, 33].