Palomar Medical Technologies, Inc. | April 1997 | Reprinted with permission

Introduction

Introduction

At present more than a half a dozen companies research groups are attempting to develop light-base hair removal systems1 which will provide quick, bulk, long-lasting (if not permanent) hair removal by treating many hairs at a time. This paper will describe the technology and clinical findings behind what is believed to be the most effective laser hair removal technique, using a long-pulse ruby laser. It should be noted, however, that other light-based technologies are under development or in current use for hair removal including the Nd:YAG laser in combination with a topical solution2, the Q-switched ruby laser3, the alexandrite laser, a non-laser flashlamp, and photodynamic therapy4.

The research as Massachusetts General Hospital’s Wellman Laboratories of Photomedicine, under the direction of Dr. R. Rox Anderson, builds on more that 30 years of investigation into the use of ruby lasers for various medical applications5. For the past 5 years, Dr. Anderson’s group has conducted both human and animal studies using a long-pulse ruby laser manufactured by Palomar Medical Technologies, Inc. (EpilaserTM) to provide long-lasting hair removal. Preliminary findings have recently been published in the first peer-reviewed article in a medical journal6. Additionally a patent7 has recently been issued to Dr. Anderson, which provides proprietary protection for the unique technology developed, by his group. The following describes that technology and the results released to date.

Equipment

The research group at MGH’s Wellman Laboratories of Photo medicine initially used a normal-mode ruby laser emitting 0.27 millisecond pules (‘pulse duration’) at 694 nanometer wavelength through a 6mm aperture (‘spot size’). These parameters were deliberately chosen to provide the optimal results within the confines of the existing state of the art.

All hair follicles within the 6mm-diameter laser beam are exposed simultaneously to laser energy. The spot size directly affects the speed of treatment since a larger spot allows treatment of a larger area with each pulse of laser light, and allows quicker overall treatment. Even a difference of a few millimeters makes a big difference in treatment time, as the diagram illustrates. As shown, a 3.6 x 3.6 cm area can be treated in less than one minute with 13 pulses using a 12mm spot size from the current EpilaserTM. This same area would require more than 60 pulses with (taking several minutes to finish) using a different system with a smaller, 6mm spot size.

Effect of Spot Size on Treatment Time
Red light at a wavelength of 694 nm has been shown to be selectively absorbed by melanin, with no effect on blood vessels. This makes the melanin in the hair follicle the targeted ‘chromophore’ for the laser light. As the melanin absorbs the laser energy, it heats the hair follicle to 60 degrees Celsius or more. This thermal effect is analogous to the effect of thermolysis (‘photothermolysis’) and acts to disable the hair’s growth mechanism.

The pulse width represents the amount of time the skin is exposed to laser energy with each pulse. This should ideally be in the range of 3 – 10 millisecond to minimize laser energy absorption in the epidermis to prevent damage to the skin surface8. The system initially used by the Wellman Laboratories’ team represented, at the time, the longest pulse width achievable in the industry. The EpilaserTM; has been redesigned. Since the initial study to emit a longer pulse of 3.0 milliseconds to provide a more effective laser hair removal system. This system represents the longest pulse width achievable thus far.

It should be noted that this system was designed with maximal safety in mind by the use of a patented7 cooling system which surrounds the optical lens that is pressed tot he skin in each laser treatment. This method cools the skin surface during each laser pulse to prevent injury to the skin surface during treatment. In addition, a variety of studies were conducted at the Wellman Laboratories to determine the optimum treatment parameters (energy settings, shaving vs. waxing, as pre-treatment, use with pre-treatment oil/lotion/emollient with specific optical and thermal properties, et.) to achieve the longest delay in hair regrowth.

Preliminary Results

In the Wellman study on humans6, the back or thigh areas of 13 adult volunteers were treated at one time. All had fair skin and dark hair. Exclusion criteria included photosensitivity, pregnancy, history of keloid formation, immunosuppression and a history of poor wound healing. Eight 2cm by 3cm sites were mapped on each volunteer, followed by photographs and hair counts. One shaved and one waxed site served as untreated controls. Each of the remaining 6 sites were treated at different energy fluence levels of 30, 40 and 60 Joules/cm² on one shaved and one waxed site. Four subjects requested use of local anaesthetic (1% lidocaine by injection). Some sites, particularly those treated at higher fluence levels, became red and swollen immediately following treatment.

Hair regrowth was defined as the percentage hairs present 1, 3, and 6 months after one treatment, compared with the number present prior to treatment. On average, after 3 months, 40% hair loss was seen, regardless of the energy fluence level used or whether skin was pre-treated with shaving or waxing. At 6 months, hair loss averaged 20 – 30%, with the best results obtained using 50 Joules/cm² on shaved areas. It should be noted that four subjects had less than 50% regrowth after 6 months following one treatment. Although some short-lived hyper and hypopigmentation was observed, these effects disappeared quickly. No scarring or change in skin texture was seen in any of the subjects.

Follow-up studies, using the EpilaserTM with the longer, more ideal pulse width and a larger spot size have since been conducted at Wellman Labs (under Dr. R. Rox Anderson), the Laser and Skin Surgery Center of New York (under Dr. Melanie Grossman) and LaserDerm Clinic in Ottawa (under Dr. Sharyn Laughlin). Each group has treated and analyzed data of approximately 50 subjects. This research, not yet published, has been included in the 510K application filed with the U.S. Food & Drug Administration by Palomar Medical Technologies, Inc. for clearance to market the Epilaser™ as a laser hair removal device. Clearance was granted, on March 5, 1997, based in part upon this data.

Current Results

At present, over 100 physicians and technologists worldwide are commercially operating the long-pulse ruby hair removal laser described above. Subjects with dark hair and all but the darkest skin tones (Fitzpatrick’s type I, II, III and IV) are considered good candidates for treatment with the EpilaserTM. All body areas except regions close to the eye can be treated9. Criteria for exclusion from treatment includes photosensitivity, pregnancy, history of keloid formation, immunosuppression or a history of poor wound healing. Treatment areas are shaved immediately prior to treatment and subjects with dark complexions are given a topical anesthetic cream (EMLA), 1% lidocaine or 5% benzocaine if desired. Some physicians are offering clients a pretreatment (5% hydroquinone cream) to reduce the melanin in the skin and prevent injury to the epidermis while extending the time for regrowth to occur.

In over 1000 test treatments on about 100 subjects, no significant complications have been observed10. While transient inflammatory and pigmentary side-effects may occasionally occur, these have been found to generally disappear spontaneously without treatment and were far less common than those found after the use of pulsed dye and Q-switched laser systems. Incidents of folliculitis were also fewer with the EpilaserTM than for other hair removal treatments.

Nonetheless, it is evident that more than one treatment will usually be necessary to provide the most long lasting results. This is particularly true since it is believed the procedure is most effective on hairs in the anagen stage, and less effective or not effective at all on hairs in the intermediate catagen or resting telogen stages. Due to this variation in hair growth cycles, this procedure should not be represented as permanent at this time.

Over the next several years, results of clinical studies being performed at ten experienced laser facilities in the United States and Canada will help determine the optimum targets for laser energy in removing unwanted or excessive hair; the effect of repeated laser treatments; the optimum intervals at which to perform re-treatment, and what method can provide truly permanent results.

References

For an overview of key photodynamic methods, see Wheeland, Dr. R.G., “Infra-red, Ultraviolet and Experimental Laser Surgery” in Cutaneous Surgery, (ed.) Dr. R.G> Wheeland, W.B. Saunders, Co., Philadelphia, Chapter 73, p. 1037 – 1056, 1994.

More detail can also be found in, Arons, I., “Laser Hair Removal: An Application whose time has come”, a white paper by Spectrum Consulting, October, 1996.

The most prevalent of these systems, Thermolase Inc.’s SoftLight™ is currently in sue for hair removal. For technical analysis, see Goldberg, Dr. D., “Topical Solution-assisted Laser Hair Removal”. Lasers Surg Med. 1995; suppl 7:47

Several companies are attempting to develop a Q-switched ruby laser for hair removal. For more information, see Copperthwaite, D., “Want to buy a Laser Epilator?”, International Hair Route, August 1996 p.48.

For a description of PDT and its use in hair removal, see Prichett, B., “A look at Photodynamic Therapy – Good News or Bad?”. The Probe, March 1997, p.2.

For a history of laser use in medical applications, see Sahoo, A., “The History of Laser Hair Removal Technology”, newsletter of the International Guild of Professional Electrologists, Spring 1997.

Grossman, Dr. M., “Damage to Hair Follicles by Normal-mode Ruby Laser Pulses”, Journal of the American Academy of Dermatology, December 1996, p.889.

U.S. Patent #5,595,568, “Permanent hair Removal Using Optical Pulses”, issued to Dr. R. Rox Anderson on January 21, 1997 and licensed exclusively to Palomar Medical Technologies, Inc.

For a discussion of how to calculate pulse width in relation to thermal relaxation time of the target structure, see item #6 above, p.893 of article.

Although virtually all body areas can be treated with the laser, Palomar Medical Technologies, Inc. believes that the laser procedure, in its best application, is complimentary with electrolysis. For a discussion, see “Letter from Palomar”, newsletter of the International Guild of Professional Electrologists, Summer 1996.

Anderson, Dr. R. Rox Anderson, “Safety and Efficacy of the Palomar Ruby Laser for Hair Removal”, Harvard Medical School, March 1997.