The success of laser resurfacing pioneered with CO2 lasers has led to a rapid proliferation of other ablative resurfacing devices including erbium lasers, microdermabrasion, and RF ablation. The Nd:YAG laser now offers a non-ablative skin treatment for patients who are not candidates for ablative procedures, or for those who have been resurfaced in the past. This technology is the result of a five-year cooperative development effort of New Star Laser, Laser Aesthetics, and the Beckman Laser Institute at the University of California, Irvine.

The Nd:YAG was developed to selectively heat a thin layer of tissue below the epidermis. Researchers were met with significant challenges creating such a system since they found that many of the current laser light sources were inappropriate as they penetrate too deeply into skin. Of further concern, energy at these wavelengths is selectively absorbed in melanin and hemoglobin making uniform heating of subsurface tissue impractical. Infrared lasers such as erbium at 2.9 micrometers, holmium at 2.1 micrometers, and CO2 lasers at 10.6 micrometers deposit all of their energy in the epidermis making them useless for selective heating of subsurface tissue.

The Nd:YAG operating at 1320nm was chosen for use in the new laser, with the first systems put into investigational use in early 1995. This wavelength falls in the practical range of 1100nm to 1600nm that penetrates easily through the epidermis and is uniformly absorbed in hydrated tissue. An additional advantage of the 1320nm is the high scattering coefficient causing the light to effectively bounce around and lose its energy before penetrating to deeper layers.

The Nd:YAG delivers up to 38 joules per square centimeter of 1320nm energy within 20 milliseconds. This causes significant heating, up to 70 degrees C, of the upper dermis with very little collateral heating. Optical energy in the 1100nm to 1600nm range can heat the epidermis enough to cause damage, especially when high energy pulses must be used. To alleviate this problem, the Nd:YAG utilizes pulsed cryogen gas to quickly cool the surface of the epidermis during treatment. Prolonged cooling chills too deeply because of thermal conduction, so a short burst of cryogen is used to selectively cool only the top 50 to 100 microns of skin. Methods of contact cooling, such as chilled plates or gels, will cool too deeply since they cannot be applied with millisecond precision and consistent thermal transfer. The Nd:YAG delevers a 20-millisecond burst of atomized cryogen, which vaporizes and cools on the way to the skin. The cryogenic mixture of cold droplets and air chills the skin surface. After a short delay of 10 milliseconds to allow any cryogen to dissipate, a 20-millisecond pulse of 1320nm energy is delivered. The surface of the skin reaches about 45 degrees C with the collagenous layer underneath about 25 degrees warmer. The Nd:YAG uses a non-contact thermometer integrated into the handpiece to monitor the skin temperature and to allow the physician the required control of treatment parameters. This temperature monitor is an absolute requirement for safe non-ablative treatment.

The Nd:YAG laser provides a unique non-invasive modality for patients who are not candidates for resurfacing because of pigmentation, other contraindications, or personal choice. The treatment requires only twenty minutes with at most a topical anesthesia. There is no wound care required, making the treatment economical for the patient and the practice. Some practices sign up patients for a long-term maintenance program.