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By Robert M. Adrian, MD, FACP --
Assistant Clinical Professor, Georgetown University Medical School,
Center for Laser Surgery, Washington DC
August, 1999
Introduction
Recent technological advances in laser hair removal have been accompanied
by a tremendous degree of public enthusiasm for this procedure.
Unfortunately, clinical studies regarding safety and efficacy of
these procedures have lagged behind the actual widespread use of
this modality throughout the world. Traditional methods of hair
removal such as shaving, plucking, waxing, and electrolysis are
associated with clinical limitations and side effects; thus the
introduction of laser hair removal has been embraced by the public
despite relatively little data regarding clinical safety and long
term efficacy.
At the present time, the primary chromophore for laser
hair removal is melanin residing in the hair shaft. In addition,
melanin residing in the inner and outer root sheath may also serve
as a secondary chromophore. In theory and most likely in clinical
treatment, the laser energy delivered to the hair shaft serves as
a heat sink, which transfers energy to the surrounding hair follicle
and perifollicular tissue. The condution of heat from the shaft
is what ultimately damages the follicle. Sufficient follicular damage
is necessary to achieve permanent hair reduction. Although multiple
factors play a role in the response of a given follicle to this
procedure, it appears that wavelength, fluence, pulse duration and
spot size are the main determinants of clinical response.
Ruby (694 nm), alexandrite (755 nm) and diode (800
nm) are currently the major wavelengths present in most laser hair
removal systems. Pulse durations of these systems vary from less
than 1 millisecond (ms) to 60 ms. Although available fluences vary,
clinically effective lasers are capable of delivering in excess
of 40 - 40 J/cm2. Over the past 4 years, we have had the opportunity
to use 5 different systems for hair removal. Results of our clinical
studies indicate that longer pulse durations are associated with
greater efficacy and with fewer post operative clinical side effects
such as blistering and pigment disturbances (1).
The ideal pulse duration for hair removal is felt
to between 10 - 50 ms (2). This pulse duration is longer than the
thermal relaxation time of the epidermis but shorter than the thermal
relaxation time of the hair shaft and follicle. Pulse durations
in this range seem to provide some degree of epidermal preservation
during treatment, allowing the delivery of higher fluences. Hair
removal lasers with short pulse durations are associated with a
higher incidence of epidermal damage in the form of blistering and
crusting. In addition, these lasers may be associated with a higher
incidence of prolonged hypopigmentation as a result of non-selective
damage to epidermal and follicular melanin. Clinical studies have
shown that longer pulse durations provide a greater margin of safety
when treating darker skin type individuals by allowing higher fluence
delivery and fewer post operative side effects.
Fluence appears to the primary consideration in the
efficacy of any system. In essence, the correct wavelength for specific
absorption by the target and ideal pulse duration for selective
photothermolysis must be accompanied by significant delivered energy
in order to achieve follicular destruction rather than temporary
laser epilation. The goal of laser hair removal is to achieve follicular
destruction rather than temporary epilation resulting from heating
of the hair shaft alone. Destruction of the hair shaft without transfer
of sufficient energy to the follicular and perifollicular tissue
will most likely provide only temporary epilation. This is most
often noted with low power scanned lasers; and may explain the rapid
regrowth seen with low energy hair removal systems.
Much debate surrounds the exact area of the follicle
which must be destroyed in order to achieve clinical efficacy. Histologically,
follicular and perifollicular coagulative changes appear to correlate
with the degree of clinical efficacy. Lack of significant follicular
damage histologically is accompanied by poor clinical efficacy.
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Figure 1.
Normal Hair Follicle. The arrow indicates the outer root sheath.
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Figure 2.
Anagen hair showing coagulative changes immediately after
treatment with LightSheer Diode Laser at 35 J/cm2.
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In 1998, Lumenis Medical introduced a new 800 nm high power, pulsed
diode laser system. Laser energy is delivered to the skin surface
by means of a water cooled, contact sapphire chill tip. The LightSheer
diode laser consists of a gallium arsenide diode array coupled to
a novel, water cooled sapphire "chill" tip that is placed
in contact with the skin during delivery of laser energy. A 9 mm
square imprint can deliver up to 60 J/cm2 in one of the products
configurations, with selectable pulse widths of 5 - 30 ms. Two pulse
width selections are available: a fixed 30 ms mode and the OptiPulse
™ mode that fixes the pulse duration at ½ the delivered
fluence (such as 40 J/cm2 with a 20 ms pulse). Pulse repetition
rate is one pulse per second (1 Hz) with a new 2 Hz system available.
Clinical studies showed the ability of this system to deliver higher
fluences with fewer clinical side effects and accompanied by significant
clinical efficacy.
Side by side comparison with the long-pulsed PhotoGenica
LPIR ™ alexandrite system (Cynosure, Chelmsford, MA) and EpiLaser
™ ruby system (Palomar, Lexington, MA) (3 ms pulse width) confirmed
the ability of active, contact cooling with the sapphire tip to
allow delivery of higher fluences in dark skin (type IV and V) individuals.
Since March of 1998 we have treated over 125 patients using this
system. Our experience regarding clinical safety and efficacy is
presented.
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Figure
3A and 3B. Patient with skin type V before and two months
after a single LightSheer treatment. The neck treatment fluence
was 25 J/cm2 and the pulse duration was 30 ms.
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Clinical Observations
A major consideration in any clinical laser procedure is patient
comfort. Most patients treated using this high power, pulsed diode
laser reported mild to moderate discomfort from diode laser impacts.
Topical EMLA (Astra, Herfordshire, England) was used in approximately
60% of cases. No patient discontinued the treatment program due
to this factor.
Clinically efficacy was judged on an individual basis
by the patient, a laser nurse, and by the treating physician. Most
patients treated experienced substantial (>60%) long term (>6
months) efficacy after 2 or 3 treatments. Post operative side effects
were limited to epidermal crusting and temporary hypopigmentation
in darker skin type patients. Over the past 10 months, greater than
125 patients have received a total of one or more treatments using
the LightSheer diode laser system. A variety of anatomic sites were
treated including lip, face, neck, axillary, bikini areas, and backs.
Our protocol involved treatment with followup at one week and one
month after each treatment. Patients were re-treated when significant
regrowth had occurred, which ranged from 1 - 3 months' time. Over
90% of patients had 2 tretments and over 70% had 3 treatments.
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| Figure 4A and 4B.
Patient with skin type II before and eight months after three
LightSheer treatments. The axilla treatment fluence was 40 J/cm2
and the pulse duration was 20 ms. |
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Figure 5A
and 5B. Patient with skin type III
before and three months after one LightSheer treatment. The
neck treatment fluence was 35 J/cm2 and the pulse duration
was 30 ms.
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Figure 6A
and 6B. Patient with skin type III
before and five months after three LightSheer treatments. The
facial treatment fluence was 35 J/cm2 and the pulse duration
was 30 ms.
Our results shown an average clearance of over 60% after 2 treatments
at monthly intervals. Fair skin type dark haired subjects experienced
excellent results; however, even skin type V patients could
be treated safely. |
Long term followup in 25 patients
showed greater than 60% clearance at 6 months after treatment. Adverse
effects were limited to erythema and edema post operatively which
lasted from 12 - 24 hours. Crusting and blistering were occasionally
seen, however, no evidence of persistent pigmentation disturbances
was noted. No textural changes or scarring was noted at any treatment
sites.
Based on our clinical and histologic
data and experience using ruby and alexandrite laser systems, it
appears that the Lightsheer diode laser system at 800 nm is quite
effective when compared to other lasers in current clinical use.
In addition, the availability of contact cooling allows the delivery
of higher fluences in darker skint type individuals expanding the
numbers of individuals who may be treated. Although other laser
systems can be used to treat darker skin type individuals, it is
the unique ability of this laser to deliver significant fluences
in dark skin type individuals that underlies its clinical advantages
in laser hair removal procedures. Although limited in scope, our
initial clinical evaluation and tissue studies would appear to indicate
that the Lightsheer diode laser provides a safe, comfortable method
for significant long term reduction in unwanted body hair.
References
1. Adrian, RM and Tanghetti, E "Clinical Evaluation of a High
Energy Long Pulse Ruby Laser for the Treatment of Unwanted Body
Hair", Lasers in Surgery and Medicine Supp. 9:36, 1997.
2. Grossman, MC, Dierickx, C, Farinelli, W et
al. "Damage to Hair Follicles by Normal Mode Ruby Lasre Pulses",
Journal American Academy of Dermatology 35:6, 889-894, 1996.
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