R. Rox Anderson, M.D.

Associate Professor of Dermatology, Harvard Medical School

Director of Research at the Wellman Laboratories for Photomedicine

INTRODUCTION

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.

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:

• Temporary hair removal for 1-3 months in all subjects, at all fluences (2).

• Permanent reduction* of hair at fluences >30 J/cm², for at least two years after a single treatment (3). Hair loss was greater in sites that were shaved (vs. wax-epilated) before treatment. "Permanent" is defined as significant and stable loss of hair for a period longer than the complete natural hair growth cycle (about one year).

*FDA clearance for claim of permanent reduction pending (Palomar EpiLaser).

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," a region of epithelial stem cells located 1-1.5 mm below the skin surface

• the "bulb," a deep, heavily-pigmented, proliferating part of anagen follicles.

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.

There are 3 distinct responses, which account for an apparently permanent (3) reduction of pigmented, coarse hair:

• miniaturization of hair follicles (dominant mechanism for LightSheer)

• decreased pigmentation of regrowing hair

• degeneration of hair follicles with replacement by fibrosis

Clinical Studies

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 range 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:

Long term hair reduction 1 year after
 treatment at 40 J/cm² fluence, 20 ms
 pulse duration, on a male's back.

 

The data in the graph above is not just "best cases", it is from all, consecutive patients treated under identical conditions. The study showed:

• 100% of patients have complete or nearly complete, temporary hair loss for 1-3 months after each treatment, at all laser fluences.

• Long-term reduction of hair occurred in the majority of patients.

• Histology (not shown) was consistent with miniaturization of hair follicles, and granulo matous degeneration of hair follicles as the dominant mechanisms for loss of terminal hair.

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.

Side-Effects

No scarring has been observed, but 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

Skin color:

Tolerated fluence is set by epidermal pigmentation. Fair-skinned patients are most easily treated. For patients presenting with a "tan" or with dark skin type, pretreatment with topical 4% hydroquinone (or other bleaching agents), sunscreen and sun avoidance for 6 weeks, should be considered prior to laser treatment.

Hair color:

Temporary (1-3 month) hair loss almost always occurs after each laser treatment, regardless of hair color. However, the effectiveness for a permanent hair reduction is strongly correlated with hair color. Blonde or white-haired patients are unlikely to experience a permanent reduction in hair. Hair loss in these patients can be maintained if desired, by treatment at approximately 3-month intervals.

Anesthesia:

LightSheer's cold handpiece greatly reduces pain during treatment. Although less-sensitive areas (back, legs, axillae) can frequently be treated without any anesthesia, topical anesthesia is generally used, e.g. tetracaine.

Technique:

Patients should not epilate or pluck hair for several weeks before treatment. Hair is shaved, usually before application of anesthetic, prior to laser treatment. After removal of anesthetic cream (if used), laser pulses at the desired fluence and spot size are delivered with the handpiece pressed firmly against the skin. The handpiece is then picked up and placed firmly on an adjacent site, until the desired area is covered. Because of active cooling, overlapping pulses to one skin site are not harmful.

Immediate responses:

The ideal immediate response for hair removal, is vaporization of the hair shaft with no other apparent effect. After a few minutes, there is perifollicular erythema and edema. If there is confluent edema or a positive Nikolski sign (epidermal separation forced by lateral pressure on the skin), fluence should be reduced.

Body site:

All body sites except the eye can be treated safely.

Safety:

This high-energy laser system is specifically designed for deep tissue penetration, and strong absorption by melanin. It is capable of causing severe retinal injury when applied near the surface of an eye. Proper eye protection must also be worn by patient and operating personnel to prevent inadvertent exposure to the eyes.

Summary

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.

References Cited

• Anderson RR, Parrish JA "Selective photothermolysis: precise microsurgery by selective absorption of pulsed radiation" Science 220: 524-527, 1983

• Grossman MC, Dierickx CC, Farinelli 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