Introduction

The development of laser-based aesthetic devices has provided patients with an appealing nonsurgical treatment alternative to address clinical aspects of photoaging skin.¹ Many treatments include skin resurfacing of the uppermost skin layers to initiate a skin regeneration process with fewer risks and complications and with a faster recovery time than conventional invasive procedures.¹

Non-ablative lasers have been developed with wavelengths in the near to mid-infrared (IR) spectrum that are selectively absorbed by water within the skin to raise the skin temperature. The heat produced by the laser coagulates structures of the epidermis and dermis, initiates a controlled wound healing response and stimulates collagen growth within the inner dermal layer.² Nonablative fractional lasers allow the delivery of energy to the skin as arrays of microscopic treatment zones (MTZs), preserving the stratum corneum and precisely targeting confined epidermal and dermal coagulations. Healing is associated with Micro-Epidermal Necrotic Debris (MENDS) located at the MTZ margins.2 Therefore, clinical results are less associated with postoperative morbidity as compared to traditional flat-beam laser treatments.³

The 1940 nm wavelength matches one of the water absorption peaks in the mid-IR band, and the tissue water absorption coefficient for this wavelength is within the range to vaporize skin tissue, but below the ablation threshold.⁴ Unlike non-ablative lasers with wavelengths in the 1320-1550 nm range or lasers used for ablative resurfacing (i.e. CO2 and Er:YAG), the 1940 nm wavelength achieves controlled superficial depths of focal damage to thermally denature the epidermis without ablating it.⁴ Histological analysis of photoaged skin treated with a fractional 1940 nm laser has shown focal damage that extended to about 200 μm in depth.⁴ Penetration depths were greater following treatment of photoaged skin with a fractional 1550 nm laser, with histological analysis showing 800 μm penetration depth at a treatment level of 88 mJ and 400 μm at 44 mJ.5 Clinical improvement was significant for reduction in diffuse pigmentation, rhytides and elastosis following treatment with the 1940 nm laser.⁴

The Candela^® 1940 nm non-ablative solid-state diode laser handpiece was developed for both the multiapplication Nordlys^® platform and the stand-alone non-ablative fractional device. The 1940 nm handpiece is FDA-cleared for general skin resurfacing procedures and benign pigmented lesions.* The handpiece is equipped with a replaceable roller tip and motion sensor, controlling the rate at which the laser delivers the MTZ arrays to the skin, as determined by the speed at which the user advances the roller across the targeted area. The treating operator has control over the scan width, energy per MTZ, and percent of coverage, while the system independently calculates the number of MTZs / scan width and the number of passes. As a safety feature to prevent multiple MTZ arrays being overlaid, the laser can only deliver energy while the roller is in motion. A low power < 1 mW red aiming beam at 650 nm helps to show the user where the treatment laser pulses will be delivered. An integrated cold air delivery system provides patient comfort.

During the second phase of an IRB-approved clinical trial**, 18 female subjects at our clinic underwent a series of 2-3 skin resurfacing treatments to photoaged skin with the 1940 nm handpiece.

Methods

Healthy male and female subjects presenting with clinically visible signs of photoaged skin were eligible to participate in the study. Subjects underwent up to three monthly skin resurfacing treatments to the face and/or body (i.e. chest) with the 1940 nm handpiece. Digital clinical photography with standardized conditions was performed at all study visits. Subjects reported on their satisfaction and graded their overall cosmetic improvement at the 1-month and 3-month follow-ups using a 5-point Likert scale (1= Not satisfied to 5= Very satisfied) and Global Aesthetic Improvement Score (GAIS) scale, from 1= Very Much Improved – Optimal cosmetic result to 5= Worse – The appearance is worse than the original condition, respectively.

Results

Subjects

A total of 18 female participants (12 Caucasians, 6 Asian) with Fitzpatrick skin type II (n=3), III (n=9) and IV (n=6) and mean age of 51±9 years (range 37-64) participated in the second part of the study for full resurfacing treatments. These subjects underwent a series of 2-3 skin resurfacing treatments to the face with the 1940 nm handpiece. Seven of the subjects were also treated in off-face areas of the chest (n=5), arms (n=1) and hands (n=1).

Treatments

Prior to full resurfacing treatment, several test spots were performed on other anatomical locations. Test spots were monitored for up to 28±7 days in order to evaluate treatment parameters for patient safety.

Topical anesthetic cream was generally applied prior to treatment using a Lidocaine 23%/Tetracaine 7% compound, EMLA™ (Lidocaine/Prilocaine) or BLT (Benzocaine/ Lidocaine/Tetracaine). Full treatment parameters were set according to physician discretion taking into consideration: test spot outcome, location of treatment, skin type and clinical indication. In general, the scan width was decreased, and the coverage increased to 30-40% when focusing on areas with discrete lesions. Face and off-face treatment parameters are summarized in Table 1.

Treatment complications were minimal, and discomfort associated with treatment was generally mild to moderate.