CLINICAL USE OF THE LIGHTSHEER DIODE LASER SYSTEM
R. Rox Anderson, M.D.
reprinted with permission
The most efficient laser in the world, is the 800 nm semiconductor diode laser. Extremely high-power diode lasers have not been available for dermatology until now. The LightSheer (TM) Diode Laser System uses state-of-the-art diode laser arrays to achieve power, efficiency, and reliability in a small package designed for versatile office use. This paper summarizes clinical efficacy and safety data for hair removal.
Unwanted, pigmented hair is a common cosmetic problem for both sexes. Until recently, the only long-lasting method of hair removal was electrolysis, which requires tedious insertion of an electrode into each hair follicle. The late Leon Goldman first described ruby laser injury to pigmented hair follicles. Over 20 years ago, Ohshiro noted hair loss from nevi after treatment with a ruby laser. At fluences affecting hair follicles however, the epidermis was severely damaged. A detailed understanding of "selective photothermolysis" (1) later emerged, and is widely applied for vascular, pigmented lesions, tattoos, and now hair removal.
The first quantitative, controlled clinical study of laser hair removal in normal human skin was reported by Grossman, et al (2). Ruby laser pulses were delivered through a cold sapphire handpiece held in contact to protect the epidermis. This pilot study showed two significant responses of dark, terminal (coarse) hair follicles, reported by the investigators in two peer-reviewed journals:
Through a cooperative license and research agreement with Massachusetts General Hospital, Palomar supported basic and clinical research by R. Anderson and colleagues, leading to FDA clearance of the first ruby laser system for hair removal, the EpiLaser. A confusing array of devices now exists for hair removal-along with speculations about actual performance. in partnership with Coherent, Palomar continues its leadership with the introduction of revolutionary technology in a versatile laser system for dermatology, the LightSheer Diode Laser System.
Effective laser hair removal requires damage to parts of the living hair follicle responsible for production and regeneration of a hair shaft.
Anatomically, there are two main target structures:
The bulge is usually devoid of melanin, but is in close proximity to the pigmented hair shaft. Plucking or wax-epilation of hair shafts prior to laser treatment significantly reduces effectiveness for long-term hair loss, but does not affect temporary hair loss (2).
All hairs go through a cycle of active growth (anagen), transition (catagen), and resting (telogen) phases. The length of hair at different body sites is governed by the duration of anagen. Duration of telogen also varies with body site, and may be as long as a year on the leg. Temporary loss of hair can therefore be achieved simply by inducing telogen. This is the mechanism for the reliable, nearly complete loss of pigmented hair for several months after each treatment with the LightSheer diode system and several other lasers. It is important to realize, however, that temporary hair loss does not predict permanent hair loss-which is what most patients seek. Reliable, controlled, quantitative, long-term clinical results are the only way to be sure of performance.
The LightSheer diode laser and its unique handpiece are specifically
optimized for treating pigmented hairs. This was accomplished
by a combination of wavelength, high power, laser pulse duration,
large spot size, convergent beam optics, aggressive skin cooling
and capability for compression of the skin during delivery of
each laser pulse. *FDA clearance for claim of permanent reduction
Studies were performed at Massachusetts General Hospital and the Laser and Skin Cancer Center of New York. Large test sites on the back or thighs of 58 consecutive patients with skin type I-V (fair to dark-skinned) and any hair color, were shaved and treated with a rance of 15-40 J/CM2 fluence, using the LightSheer diode laser. Baseline and subsequent regrowing terminal hair counts were taken from high-quality digital images of each site. Adjacent, untreated control sites were also counted. Results from one and two treatments given approximately two months apart, were compared in each patient, at each fluence. Treatment at any body site elected by the patient was also given. Efficacy is best appreciated as the percentage of terminal hair which regrows over time, shown below for different fluences:
Figure 1. Hair regrowth followed for one year after 1 and 2 treatments, at a fluence of 40 J/cm2. Shaved control sites (right hand cluster) received no laser treatment.
The data in Figure 1 is not just "best cases" it is from all consecutive patients treated under identical conditions. The study showed:
About 70% of patients with black, brown, auburn, or red hair had long-term hair reduction, whereas only about 10% of patients with blonde hair had long-term hair reduction. The degree of long-term hair reduction was fluence-dependent
No scarring has been observed, but it is wise to warn patients that this might occur rarely after any skin treatment. The most common side-effect, seen in about one patient in six, is transient hyper- or hypo-pigmentation, which clears in 1-6 months. Pigmented lesions such as lentigines and freckles may become permanently removed. These pigmentary changes are fluence- and skin type-dependent; the ideal patient for laser hair removal has dark hair and fair skin. Moderate pain, perifollicular erythema and edema occur commonly and resolve within a few days after each treatment. Local blisters rarely may occur at high fluences in dark-skinned patients.
TREATMENT GUIDELINES - HAIR REMOVAL
The LightSheer Diode has been shown to be safe and effective for pigmented hair removal. The actively-cooled handpiece combined with long pulse duration and smooth pulse structure, reduces epidermal injury.
Anderson RR, Parrish JA "Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation" Science 220: 524-527, 1983
Grossman MC, Dierickx CC, Farineiii WA, Flotte Tj, Anderson RR "Damage to hair follicles by normal-mode ruby laser pulses" J Amer. Acad. Dermatol 35: 889-894, 1996
Dierickx CC, Anderson RR "Permanent hair removal by normal-mode ruby laser" Arch Dermatol. 1998 (in press)
Anderson RR, Parrish JA "Optics of human skin" J. Invest. Dermatol. 77:13-19, 1981
Note., In addition to hair, removal, the LightSheer Diode Laser System is also cleared for the treatment of leg veins.
R. ROX ANDERSON