Wavelength 1720 nm and Sebaceous Glands

An SP in vitro study to determine wavelengths potentially able to target sebaceous glands was performed by Sakamoto and colleagues. Absorption peaks near 1210, 1728, 1760, 2306, and 2346 nm were found with the use of a free-electron laser pulsed at an infrared CH(2) vibrational absorption wavelength band on natural and artificially prepared sebum. Laser-induced heating at 1710 and 1720 nm was about 1.5-fold higher in human sebaceous glands than in water. Histology of skin samples exposed to pulses of approximately 1700 nm and 100 to 125 milliseconds showed evidence of selective thermal damage to sebaceous glands. With the use of wavelengths that more specifically target sebum, the investigators hypothesized that SP of sebaceous glands, another part of hair follicles, may equate to the success of permanent hair removal via laser.

In a pilot clinical study to evaluate the efficacy of a novel 1720-nm laser in the treatment of sebaceous hyperplasia, 4 patients underwent a test spot, followed by 2 full treatment sessions using the 1720-nm laser (Del Mar Medical Technologies, Del Mar, CA, USA). A 400-μm fiber, with a mean fluence of 45 J/cm ² , spot size of 750 μm, and pulse duration of 50 milliseconds was used to deliver the energy. The desired end point was a change from pretreatment granular yellow appearance to a creamy-white smooth surface. Damage to adjacent normal skin showed no change until the pulse duration exceeded twice that of the sebaceous hyperplasia. A panel of 3 independent dermatologists blinded to the date of the photographs evaluated the photos and scored them based on a global assessment comprising: (1) lesion diameter, (2) lesion height, and (3) lesion color. Many of the lesions resolved almost completely after a single treatment, and no additional treatment was required. There was a mean global improvement of 3.9 (3 = 51%–75% improvement and 4 = 76%–99% improvement). Crusts were noted by all patients, which resolved within 10 days.

Complete heating of the sebaceous gland and sparing of the surrounding skin offered by the investigated device resulted in clinically apparent improvement with a minimum of adverse effects. Further studies are warranted, with larger sample sizes, to investigate the efficacy of this novel wavelength and possible future wavelengths in the SP of sebaceous glands and its impact in the improvement of sebaceous hyperplasia, ectopic sebaceous glands, acne vulgaris, and laser hair removal.

Perhaps there is also hope beyond the use of lasers for SP of sebaceous glands, such as that seen with microfocused ultrasound with visualization (MFU-V) for the treatment of moderate to severe facial acne. Although the mechanism of action remains unclear, it is hypothesized that with the use of 1.5-mm and 1-mm depth probes, focal thermal coagulation points are being delivered into sebaceous glands, rendering them not as active. In a pilot study in which 10 subjects received 3 treatments, 14 days apart with MFU-V, a significant decrease in sebum, as measured by a sebumeter (Courage-Khazaka, Cologne, Germany), was noted over the forehead, cheeks, and chin 60 days after treatment. Eighty percent of subjects had a decrease in total acne lesion count at 60 days, and 100% of subjects showed a decrease at 180 days after the last treatment. Data from this pilot trial suggest that MFU-V may prove to be a promising novel treatment option to improve acne clearance in those with moderate to severe inflammatory acne.

Wavelength 1210 nm

Absorption peaks near 915, 1210, 1400, 1720, and 2346 nm have been demonstrated for lipids. A study to evaluate the histologic changes over time of a novel noninvasive treatment with a 1210-nm laser with surface cooling, to more selectively target fat, was performed on 8 patients before abdominoplasty. Skin evaluations and blood monitoring were tracked for safety. Postabdominoplasty tissue was evaluated histologically at 2 days, 1 week, and 1, 3, and 6 months after laser treatment with energy doses ranging from 120 to 200 J/cm ² and from 220 to 480 J/cm ² for 40-second and 160-second pulses, respectively. A decrease in nitroblue tetrazolium chloride staining showed damaged zones, predominantly in the hypodermis, approaching 6 mm in thickness. Laser damage to the lipid barrier membrane was confirmed by a decrease in perilipin staining, and caspase staining confirmed apoptotic adipocytes at the periphery of necrotic tissue. Chronic inflammatory cells were still present at 6 months after laser treatment. Damage to the lower dermis was higher for the 40-second pulse than for the 160-second pulse. The investigators concluded that significant zones of fat reduction in hypodermal necrosis could be achieved, while including or avoiding damage to the lower dermis depending on the settings used. Clearance of the damaged adipocytes proved slow, with residual damage still present at 6 months.

A clinical trial was performed to evaluate the use of the 1210-nm wavelength (ORlight, Potters Bar, UK) for fat preservation, as the investigators describe this wavelength as being capable of selective photothermostimulation (PSP), a concept whereby the wavelength has the ability to stimulate adipocytes and mesenchymal cells of the subcutaneous tissue. One hundred two patients were treated with the 1210-nm diode laser and followed. Samples of aspirated tissue were sent for histologic analysis to determine whether any alteration of adipocytes occurred with treatment. Histologic analyses revealed a 98% preservation of aspirated adipocytes. The investigators hypothesize that this selective PSP and preservation of the integrity of adipocytes makes this laser wavelength ideal when performing laser-assisted liposculpture followed by fat grafting or breast reconstruction.

There may be a place for the addition of another wavelength that has a greater absorption affinity for lipid-rich tissue than the wavelengths of lasers presently on the market. Further studies, with larger sample sizes, will help determine the benefit of this novel wavelength in laser-assisted lipoplasty and, perhaps, the removal of large lipomas.

1565-nm Erbium-Doped Laser

The development of fractional photothermolysis (FP) is a milestone in the history of laser technology and cutaneous resurfacing. FP refers to the creation of pixilated columnar zones of thermal injury, referred to as microthermal treatment zones, which are delivered to the dermis, with resultant coagulation necrosis followed by collagen remodeling and synthesis. Selective injury of the dermis with relative or absolute sparing of the epidermis was established and termed “nonablative.” Unlike traditional nonablative infrared lasers, nonablative fractionated lasers (NAFL) treat only a fraction of the skin, being able to leave up to a maximum of 95% of the skin uninvolved. This targeting allows the undamaged surrounding tissue to act as a reservoir of viable tissue, permitting rapid epidermal repair. In 2003, the first NAFL was introduced to the market based on the concept of FP, namely the fractionated 1550-nm erbium-doped “fraxel” laser, now called the Fraxel Re:Store (Fraxel Re:Store, Solta Medical, Hayward, CA, USA).

NAFL can be used to treat a variety of conditions, including fine lines and wrinkles, dyschromia, striae, and scars. The benefits are minimal downtime and relatively low risk of adverse effects. Since the inception of NAFL, a variety of NAFLs with wavelengths in the near-infrared range have surfaced as a result its popularity, including the Q-Switched 1064-nm Nd:YAG (HarmonyXL Alma Lasers, Buffalo Grove, IL, USA), the 1440-nm Nd:YAG (Affirm; Cynosure Inc, Westford, MA, USA and Palomar Starlux, Artisan, Icon; Palomar Medical Technologies, Burlington, MA, USA), 1440/1320-nm Nd:YAG (Affirm Multiplex; Cynosure), 1440-nm diode (Clear and Brilliant System; Solta Medical), 1540-nm erbium:glass (Palomar Starlux, Artisan, Icon; Palomar Medical Technologies), 1927-nm thulium (Fraxel Re:Store Dual; Solta Medical), and 1927-nm diode (Clear and Brilliant Perméa handpiece on the Clear and Brilliant System; Solta Medical).

A new NAFL with no disposable tips, with a handpiece that allows real-time “cool-scanning” in a stamping fashion, was recently approved by the Food and Drug Administration (FDA) (M22 [ResurFx module]; Lumenis, Inc, San Jose, CA, USA). Infrared laser energy at 1565 nm has a slightly lower absorption coefficient for water than that of 1550 nm (9/cm and 8/cm, respectively), leading to marginally greater dermal penetration. A wide variety of shapes, densities, and sizes of patterns are offered, ranging from 5 to 18 mm. Energy level ranges from 10 to 70 mJ with density ranging from 50 to 500 spots/cm ² . Preliminary results of a 2-center trial treating a total of 30 subjects with visible rhytides (Fitzpatrick Wrinkle Score of 3–6) and/or striae alba (present for >1 year), who received a single-pass treatment monthly for 3 consecutive treatments, shows appreciable results and high patient satisfaction. Future studies to determine its efficacy in the treatment of scars and dyschromia, as well as to compare its performance with that of other NAFL devices, will optimize its application.

1940-nm Nonablative Fractionated Laser

1940 nm is a novel wavelength that has a higher absorption coefficient for water than other nonablative wavelengths (1410–1550 nm), and is weaker than ablative wavelengths. A new fractional 1940-nm laser comprises thulium rod pumped by a pulsed alexandrite laser. The fractional patterns are generated by 3 separate hand pieces (2 dot and 1 grid geometries) whereby a larger beam is broken up into smaller microbeams by a diffractive microlens system. Its depth of penetration extends approximately 200 μm deep to the surface. In a pilot trial of 11 patients with facial photodamage, patients received 3 full-face treatments, carried out in 2 passes, 4 to 6 weeks apart, using topical anesthesia and cold-air cooling for patient comfort. Outcome assessments included changes in pigment, rhytides, laxity, texture, and elastosis. Three months after the last treatment, mean texture scores were unchanged, rhytides were reduced by 15% ( P = .05), and pigment improved by 30% ( P = .05). Downtime from the procedure ranged from 3 to 5 days and the only adverse event reported was mild vesiculation in 2 patients.