Erbium: yttrium aluminum garnet lasers (Er:YAG) were first introduced as bone-cutting lasers in the late 1980s. These lasers are seeing some resurgence in the cutaneous resurfacing market, with the introduction of new modified delivery methods and alternative wavelengths.
The target chromophore for the Er:YAG is water, primarily intracellular water. At a wavelength of 2,940 nm, the Er:YAG is the infrared wavelength most absorbed by water. This wavelength is approximately 10 to 15 times better-absorbed by water than the CO2 wavelength (10,600 nm).
Penetration of a traditional short-pulsed Er:YAG laser is on the order of approximately 10 to 25 microns, due to the trapping of the light energy by water located superficially in the skin. This depth can be increased or decreased based on energy level, number of pulses or passes, pulse duration and delivery mode (fractional vs. traditional).
Originally introduced as a short-pulsed system, the Er:YAG was initially considered as a treatment for milder cases of photodamage. Due to its more promising safety profile, it was thought that the Er:YAG would replace the CO2 for facial laser resurfacing. These short-pulsed systems were predictable and safe, but results for more extensive photodamage were not impressive. The short pulse width (approximately 300 microseconds) results in ablation without thermal damage. This lack of thermal damage may be the reason for the more modest improvement of rhytids.
The Er:YAG was then modified by changing the pulse delivery. Lengthening the pulse width, or providing a dual pulse, helps increase the depth of injury and also provides some tissue coagulation, resulting in better hemostasis. These new "modified" systems are more effective for wrinkle reduction. However, the long-pulsed Er:YAG treatments seem to carry more risk of post-procedural erythema and pigment irregularities (Kim et al. Lasers Surg Med. 2005). Despite this, it is still safer than traditional CO2 resurfacing.
Both off-face resurfacing and treatment of darker skin types are feasible with the Er:YAG. Those with darker skin types are always at higher risk for complications, and settings should be adjusted accordingly. Increasing the number of passes can also result in improved efficacy. At four to eight passes, dermal remodeling can be achieved with a single session of Er:YAG resurfacing (Trelles et al. Lasers Med Sci. 2009).
Variable pulsed Er:YAG systems can result in tissue coagulation up to 400 microns in depth, with an added thermal damage of up to 100 microns in depth. Off-face resurfacing is also possible with the Er:YAG devices, yet they must be used with caution. Data as to the most effective and safe parameters is not available for off-face treatment.
As with any laser, each device has its own ideal settings, and recommended fluence levels do not translate between devices, even though they may be of the same wavelength.