Biomedical Engineering Reference
In-Depth Information
theory of pain transmission, it stimulates pressure receptors in
the skin immediately prior to fi ring of the laser pulse, thereby
blocking activation of pain fi bers. PSF is just beginning to be
incorporated into commercially available lasers (Table 5.1).
A recent study of LHR using an LPDL with a large spot size
and vacuum-assisted suction showed that the majority of sub-
jects reported feeling no pain at all or up to moderate pain
without the use of skin cooling or topical anesthetics (44).
Notably, none of the subjects in the study reported experienc-
ing severe or intolerable pain.
of hair follicle anatomy and physiology, pearls for patient selec-
tion and preoperative preparation, principles of laser safety, an
introduction to the various laser/light devices, and a discussion
of laser-tissue interactions that are vital to optimizing treat-
ment effi cacy while minimizing complications and side effects.
acknowledgments
This chapter is modifi ed and updated from Ref. 6. It also repro-
duces images from Christine Dierick's chapter on laser hair
removal in Goldman MP, ed. Cutaneous and Cosmetic Laser
Surgery. St. Louis: Mosby, 2006.
Home Use Laser and Light Source Devices for Hair Removal
In recent years, a number of devices have been developed that
seek to provide subjects with the ability to achieve hair removal
at home. These devices are based on IPL, laser, and thermal
technologies that target the hair follicle for destruction. These
devices include Spa Touch (Radiancy), Tria (SpectraGenics),
and no!no! (Radiancy).
The evidence behind such devices is scant and limited to
small noncontrolled studies (59-61). In addition, the risk for
devastating eye injuries with improper use of laser- and IPL-
based devices and lack of medical training raises a dilemma of
how much autonomy a patient should have with potentially
harmful devices. Nonetheless, the appeal of having a personal
device to remove unwanted hair in the privacy of one's home
without the expense and inconvenience of multiple dermatol-
ogist or spa visits will likely drive the development of addi-
tional home use devices.
references
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by selective absorption of pulsed radiation. Science 1983; 220: 524-7.
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controlled study of efl ornithine cream combined with laser treatment
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Alternative Technologies for Hair Removal
Photodynamic therapy with aminolevulinic acid (ALA) has
been shown in a small pilot study to result in up to 40% hair
loss with a single treatment, although wax epilation was per-
formed prior to treatment in this study (62).
Electro-Optical Synergy (ELOS) technology combines elec-
trical [(conducted radiofrequency (RF)] and optical (laser/
light) energies (63). A handful of devices based on this technol-
ogy have been produced (Table 5.1). The theory behind ELOS
is based on the optical component (laser or IPL) heating the
hair shaft, which then is thought to concentrate the bipolar RF
energy to the surrounding hair follicle. Based on this combina-
tion, lower fl uences are needed for the optical component,
thereby suggesting it might be well tolerated in all Fitzpatrick
skin phototypes, and potentially effective in the removal of
white and poorly pigmented hair. A study of 40 patients (Fitz-
patrick skin phenotypes II-V) with varied facial and nonfacial
hair colors were treated with combined IPL/RF ELOS technol-
ogy. An average clearance of 75% was observed at 18 months
following four treatments. No signifi cant adverse sequelae were
noted and there were no treatment differences between patients
of varying skin types or hair color (64). Pretreatment with ALA
prior to use of a combined IPL and RF device has been shown
to further augment the removal of terminal white hairs (65).
In conclusion, hair removal has made a dramatic shift from
an art to a science based on the theory of selective photother-
molysis. Since the fi rst reports of selective hair removal in 1996
by Anderson and colleagues (5), there has been a tremendous
explosion in the number of devices used for LHR and making
LHR the most commonly requested cosmetic procedure in the
world. This review provides the reader with the fundamentals
