Pulsed Dye Laser

Laser systems operating in the mid-infrared portion of the electromagnetic spectrum, including the 1320 nm Nd:YAG, 1450 nm diode, and 1540 Er:Glass lasers, possess optimal wavelengths for water-based non-ablative skin remodeling [52]. The majority of ultraviolet induced sun damage occurs at dermal depths of 100–400 um and, because the water absorption coefficient is low at wavelengths longer than 700 nm, infrared lasers (>1000 nm) are able to better deliver energy at these tissue depths [44].

To protect the epidermis, dynamic cooling is employed. The handpiece contains a thermal sensor to assist in maintaining the epidermal temperature below 50°C. At 40–45°C, the dermis is heated to a temperature reached of 60–65° [44, 53]. The latest generation of the 1320 nm Nd:YAG laser (CoolTouch II, ICN Pharmaceuticals, Costa Mesa, CA) delivers energies ranging 28–38 J/cm² with a pulse duration of 350 us through a 10 mm spot size handpiece. Treatments are usually performed every month for a series of at least three sessions. Multiple studies have shown efficacy in the treatment of rhytides and atrophic facial scars with only mild edema and erythema post-procedure [53–57].

The 1450 nm diode laser (SmoothBeam, Candela Corp., Wayland, MA), which shortly followed the development of the 1320 nm Cool- Touch laser, also targets water in deep dermal tissue. At the 1450 nm wavelength, lower peak powers are generated so delivery at longer pulse durations is necessary to achieve optimal fluences. For epidermal protection, tissue cooling is applied at brief intervals before, during, and after laser exposure [58]. In recent clinical trials, the SmoothBeam laser was shown to be effective in the treatment of facial and neck rhytides, acne, and atrophic scars [58–62]. Periocular rhytides, in particular, appear to be most amenable to 1450 nm diode laser irradiation, with marked clinical improvement observed after a series of four treatments [58, 59]. Fluences used for treatment ranged 12 to 14 J/cm² with a 6 mm spot. Maximal clinical improvement is delayed for 6 months after the series of treatments, presumably because of slow collagen remodeling and synthesis.

A study comparing the 1320 nm Nd:YAG to the 1450 nm diode laser for treatment of atrophic acne scars revealed that the 1450 nm laser effected more significant change in the scar appearance and skin texture [57]. Both mid-infrared lasers, however, induced clinical improvement. With the additional positive effect of the 1450 nm diode laser on active acneiform lesions [62], this system may be preferable for those patients with concomitant acne and atrophic facial scars.

Like the two aforementioned infrared lasers, the 1540 nm erbium-doped phosphate glass (erbium glass) system targets deep dermal water but is least absorbed by melanin, offering a potential advantage to the other nonablative lasers when treating darker skin types. The 1540 nm erbium glass laser has been used successfully to treat facial rhytides at 10 J/cm through a 4 mm collimated beam (Aramis, Quantal Medical, France) [63,64].