Download Treatment of Neck Lines and Forehead Rhytids

ORIGINAL ARTICLE
Treatment of Neck Lines and Forehead Rhytids with a
Nonablative 1540-nm Er:Glass Laser: A Controlled
Clinical Study Combined with the Measurement of the
Thickness and the Mechanical Properties of the Skin
S ERGE D AHAN , MD, n J EAN M ICHEL L AGARDE , P H D, w V IRGINIE T URLIER , MSc, L AETITIA
C OURRECH , MSc, w AND S ERGE M ORDON , P H D z
Dermatology and Laser Center, Clinique St Jean du Languedoc, Toulouse, France; wCenter Jean Louis Alibert,
CERPER, Institut de Recherche Pierre Fabre, Toulouse, France; and zUPRES EA 2689, INSERM IFR 114, Lille, France
n
Nonablative remodeling has been recently
proposed as a new, no-down-time, antiaging treatment.
OBJECTIVE. The objective was to evaluate the efficacy and
safety of nonablative skin remodeling with a 1540-nm Er:Glass
laser on neck lines and forehead rhytids.
METHODS. Twenty female patients (mean age 45 years) were
enrolled. Skin thickness and mechanical properties were
measured before the first treatment, 1 month after the third
treatment, 1 month after the fifth treatment, and 3 months after
the fifth treatment.
RESULTS. All patients reported an improvement in both skin
tone and texture. Using ultrasound imaging, dermal thickness
BACKGROUND.
of neck and forehead increased, respectively, by 70 13 lm
(po0.001) and 110 19 lm (po0.003). A dramatic increase of initial stress of the forehead skin (firmness) was
obtained, from 7.62 3.68 before treatment to 16.68 7.44
3 months after the fifth treatment (po0.0002). No immediate
or late adverse effects were noted throughout the treatment
regimen.
CONCLUSION. This study demonstrates that irradiation with a
1540-nm Er:Glass laser emitting in a pulsed mode and coupled
with an efficient contact cooling system increases dermal
thickness and firmness, leading to a clinical improvement of
neck lines and forehead rhydits.
SERGE DAHAN, MD, JEAN MICHEL LAGARDE, PHD, VIRGINIE TURLIER, MSC, LAETITIA COURRECH, MSC, AND
SERGE MORDON, PHD HAVE INDICATED NO SIGNIFICANT INTEREST WITH QUANTEL MEDICAL. THE SUPPORT
OF QUANTEL MEDICAL WAS RESTRICTED TO THE LOAN OF THE LASER.
A GROWING majority of patients are interested in
the potential of nonablative skin remodeling to smooth
away their wrinkles. This procedure induces a spatially
determined, controlled thermal dermal damage leading
to subsequent collagen remodeling with epidermal
preservation. The use of numerous lasers and intense
pulsed light systems has been reported for this
indication. Among them, the Er:Glass laser has
demonstrated its efficacy and its lack of adverse
effects. In 2001, Fournier and colleagues1 published
a preliminary clinical study with histology, profilometry, and ultrasound imaging involving 60 patients with
a follow-up at 6 months where objective data
correlated with visible clinical improvement. The
efficacy of the laser was confirmed by a recent study
by Fournier et al. with 14 months’ follow-up.2 More
Address correspondence and reprints requests to: Serge Mordon, PhD,
UPRES EA 2689, INSERM (French National Institute of Health and
Medical Research) IFR 114, Pavillon Vancostenobel, Lille University
Hospital, 59037 Lille Cedex, France, or e-mail: [email protected].
recently, Lupton and coworkers3 also observed a
gradual clinical and histologic improvement with this
laser.
The purpose of this study was to carry out a longterm evaluation of the efficacy and safety of nonablative skin remodeling of neck lines and forehead
rhytids using this 1.54-mm Er:Glass laser through a
controlled clinical study. Skin thickness and skin
firmness were measured to quantify the degree of
improvement.
Materials and Methods
Laser
The 1540-nm Er:Glass laser (Aramis, Quantel Medical,
Clermont Ferrand, France) wavelength is obtained
from a specific codoped Yb-Er:phosphate glass material, optimized for high efficient pumping absorption.
Flashlamp pumped, its wavelength (1.54 mm) is highly
absorbed by water, making it particularly interesting
r 2004 by the American Society for Dermatologic Surgery, Inc. Published by Blackwell Publishing, Inc.
ISSN: 1076-0512/04/$15.00/0 Dermatol Surg 2004;30:872–880
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DAHAN: REMODELING OF NECK LINES AND FOREHEAD RHYTIDS WITH A LASER
for dermatologic applications (Patent 5.897.549). The
laser head is optimized to reduce pump radiation
absorption by water and it is based on high diffusion
materials. The design of the laser cavity is simple and
features high efficiency and good stability. It works in
normal mode delivering up to 5 J in 3 ms. It can work
either in single-shot mode or in a pulse-train mode with
repetition rate at to 2 Hz. The beam is delivered by an
optical fiber. An aiming beam is provided by a red laser
diode. Internal cooling avoids water connection and
only standard power outlet (10 A) is required. The
system is compact, monitored by a microprocessor
assuming high reliability and compliant with all
medical norms (US and CE).
For this study, the laser was tuned at 10 J/cm2 per
pulse. The treatment consisted of three pulses (30/cm2
cumulative fluence) at 2-Hz repetition rate applied
with a 4-mm spot handpiece and an integrated contact
cooling system.
Cooling System
The skin was cooled using the Koolburst handpiece
(Quantel Medical). Purified tetrafluorethane cryogen
circulates around a cryosapphire with an 8-mm
viewing area. The sapphire is put in direct contact
with the skin and includes real-time temperature
monitoring for immediate feedback. The handpiece
is connected to an electronic unit, ensuring temperature stability within 11 during treatment. In this
study, cooling temperature was set at 151C and
contact was maintained for at least 2 sec before firing
the laser.
Clinical Protocol
For each patient, age, sex, and phototype were
recorded. Phototype was evaluated using Fitzpatrick’s
classification (I to VI). All neck and forehead areas
involved in this protocol were free of any prior
aesthetic treatments (lifting, filling injections, peelings,
lasers, etc.).
Contraindications included history of other laser
procedure on the neck or on the hands, collagenrelated diseases, treatment by Accutane completed or
arrested within 2 years, keloid, pregnancy, peeling,
dermabrasion, fillings, and antiaging treatments
(creams, tablets)
Only neck lines and forehead rhytids were included
in this study. For each patient, the treated area was
traced on a sketch and kept in their file. This sketch
was used to reproducibly position the probes used for
the measurement of thickness and mechanical properties of the skin.
873
Unwanted effects were systematically noted before
and after every treatment (1—none, 2—erythema, 3—
edema, 4—blister, 5—hyperpigmentation, 6—hypopigmentation, 7—bruising, 8—skin whitening, 9—
scarring). Pain was evaluated by the patient on a scale
of 1 to 4 and recorded (1—none, 2—minimal, 3—
bearable, 4—unbearable). The patients were also
asked to give their overall satisfaction and skin tone
and skin texture was quantified on a scale of 1 to 10
(0—unsatisfied, 5—moderately satisfied, 10—extremely satisfied). Overall 100 treatment sessions were
realized
Photographs
Performed in the Center Jean Louis Alibert (Toulouse,
France), photographs were taken before the first
treatment, 1 month after the third treatment, 1 month
after the fifth treatment, and 3 months after the fifth
treatment. To standardize the pictures, all photographs
were taken with a digital camera (Kodak-modified
Nikon N90s, Model DCS420) set at a constant
exposure (1/125 shutter speed and f/16 aperture).
Lighting conditions were kept constant by using a light
box (Multiblitz 75 75 cm), connected to a flash
Multiblitz Profilux 600.
Ultrasound Imaging
Ultrasound is a unique quantitative and qualitative
tool widely used to evaluate the efficacy of cosmetics
on the skin. This technology is used to measure
changes in skin thickness related to product performance. Ultrasound uses high-frequency sound waves
to create an image of the skin and its immediate
substrate. A high-frequency signal is sent out from the
emitting source into the skin. When the sound wave
strikes a tissue it sends back an ‘‘echo,’’ so for each
tissue layer another echo is created. The size or
amplitude of each of these echoes in conjunction with
the difference in time it takes for the ‘‘echoes’’ to return
to the emitting source provides the information needed
to produce a two-dimensional representation of the
skin. In this study, skin thickness was determined with
a high-resolution B-mode real-time ultrasonic scanner
(DermCup 2020, GIP Ultrasons, Tours, France). High
resolution is obtained by means of a strongly focused,
20-MHz center frequency transducer, with a 25-MHz
bandwidth at 6 dB. This system displays 10 frames
per second. The scanning field is 6 mm (laterally) 5 mm (axially). The resolution is 0.3 mm (laterally) and 0.08 mm (axially). Once the two-dimensional
picture has been created it is possible to see the
structure of the skin and measure the thickness of the
epidermis, the dermis, and the subcutaneous fat. The
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DAHAN: REMODELING OF NECK LINES AND FOREHEAD RHYTIDS WITH A LASER
system calculates the distance between two points with
an accuracy of 0.01 mm.
Firmness
25
p < 0.001
Measurement of the Mechanical Properties of the
Skin
An echorheometer (Pierre Fabre, Toulouse, France)
was used to measure the initial stress of the skin. The
echorheometer combines a suction system and an
ultrasound scanner. The principle of the apparatus is
based on the creation of a partial vacuum in a small
cylinder partly filled with water, causing skin deformation through suction. The resulting vertical displacement of the skin is measured using a fixed ultrasound
transducer (20 MHz).
The echorheometer is different from the cutometer
developed by Courage and Khazaka usually used to
study the elasticity of the skin. The advantage of the
echorheometer is that the firmness constant is derived
form a continuous displacement/pressure curve and
from one or two values’ strain resulting from applied
stress. This allows the initial stress in the skin to be
separated from the applied stress, thus measuring the
firmness of the skin. This technique takes into account
the skin’s thickness, which varies from one person to
another and greatly affects its behavior under applied
stress, using the high-resolution ultrasound technique.
Consequently, the initial stress is measured at the same
time as is Young’s modulus. It correlates to the initial
tension (N/m) divided by the thickness of the skin.
This parameter is independent of the direction of
Langer’s lines. Being an average of the initial tension of
the skin in all directions (applications of suction on a
circular area of the skin), it is more reproducible,
which is primordial when evaluating dermal alterations or treatment efficacy.4
This measurement gives a quantified value of skin
firmness. Initial stress parameters are used in the
cosmetic industry.5–7 It has been shown that this
parameter reaches its maximum at age 20 and
progressively decreases (Figure 1). To compare the
data obtained in this study to previous studies,
measurements were restricted to the forehead.
Procedure and Follow-Up
This clinical study was approved by the local ethical
committee. All patient first signed a consent form and
were then treated every month, for 5 months, with a
subsequent 3 months’ follow-up. The duration of the
study was 7 months. The study protocol conformed to
the ethical guidelines of the 1975 Declaration of
Helsinki.
For each session, digital pictures before and after
were taken and pain and side effects were recorded.
Initial stress (K Pascal)
23
21
Males
Females
p < 0.001
19
17
15
13
11
9
7
5
0-5
5-10 10-15 15-20 20-30 30-40 40-50
Figure 1. Initial stress variation (skin firmness) as a function of age
from Diridollou et al.41
Measurement of skin thickness and mechanical properties were performed before the first treatment, 1
month after the third treatment, 1 month after the fifth
treatment, and 3 months after the fifth treatment at the
Center Jean Louis Alibert, Toulouse. Because melanin
absorption at 1.54 mm is very low, patients did not
require sun protection, even during summer. No
anesthesia was performed. The treatment was performed as follows: (1) rhydits were traced using
juxtaposed 4-mm spots, one spot consisting of three
pulses and (2) the skin between rhydits was covered by
juxtaposed 4-mm spots. For forehead treatment, 50 to
70 spots were usually required. For neck treatment, 80
to 100 spots were applied. Because no clinical end
point was visible with this technique, a slight overlap
was accepted
Data Analysis
Student’s statistical t tests were used to highlight the
results.
Results
The enrollment consisted of 20 female patients, ages
ranging from 25 to 56 years (mean age 45 years).
Results were obtained 1 month after the third
treatment, 1 month after the fifth treatment, and 3
months after the fifth treatment. Their ages ranged
from 34 to 67 years (mean age 47 years). Phototypes
treated were from I to IV. Overall 100 treatment
sessions were realized.
The treatment was well tolerated by all patients and
anesthesia was never required. No side effects were
reported, all patients scoring 1. Using the laser with
the parameters given above, no immediate visible
effects were observed: no swelling, no erythema
(except a very transient one for a few seconds from
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DAHAN: REMODELING OF NECK LINES AND FOREHEAD RHYTIDS WITH A LASER
875
the cooling device), and no bleaching. There were also
no late visible side effects like dyschromia (this
wavelength has minimal melanin absorption), crusting, or blistering. Because treated and untreated sites
are indistinguishable from one another, the search for a
visible clinical end point was not possible.
Patient’s Satisfaction, Skin Tone, and Skin Texture
(Figure 2)
Three months after the last treatment, all patients in
the study were extremely satisfied: score 10 for both
neck and forehead. They were also very satisfied by the
improvement of the skin tone: score 8 for the neck and
9 for the forehead. They were moderately satisfied by
the improvement in skin texture: score 6 for forehead
and score 5 for neck.
Ultrasound Imaging (Figure 3)
Dermal thickness increased as a function of time. On
the neck, preoperative dermal thickness was 1.42 0.14 mm. It progressively increased to 1.55 0.15 mm
at 1 month after the third treatment, and 1.59 0.15 mm at 1 month after the fifth treatment. Three
months after the fifth treatment, dermal thickness
slightly decreased to 1.53 0.11 mm. This value was
significantly different from the preoperative measurement (po0.001). Figure 3 is one example of ultrasound
imaging performed on the neck. Preoperative thickness
was 1.38 mm. One month after the fifth treatment, a
0.39-mm thickness increase was observed (1.77 mm).
Similarly, on the forehead, preoperative dermal
thickness was 1.79 0.19 mm and progressively
increased to 1.92 0.20 mm at 1 month after the
Figure 3. Ultrasound images: Patient 15 neck: before treatment (A)
and 1 month after five treatments (B).
third treatment and to 1.94 0.21 mm at 1 month
after the fifth treatment. Three months after the fifth
treatment, dermal thickness slightly decreased to reach
1.86 0.18 mm. This value was also significantly different from the preoperative measurement (po0.003).
Measurement of the Mechanical Properties of
the Skin
The progressive increase of initial stress, as obtained
on the forehead, is illustrated in Figure 4. Results
are as follows: before operation, 7.62 3.68 KPa; 1
month after the third treatment, 14.06 7.19 KPa;
1 month after the fifth treatment, 15.36 8.62 KPa;
and 3 months after the fifth treatment, 16.68 7.44 KPa. When the final measurement is compared
to the initial one, a statistically significant improvement is obtained (po0.0002).
Analysis of Clinical Pictures
In most cases, digital photographs initially showed a
progressive and globally mild visual improvement after
19
9
overall satisfaction
8
skin tone
7
skin texture
6
5
4
3
0 - Unsatisfied
2
5 - Moderately Satisfied
1
10 - Extremely Satisfied
0
neck
forehead
Figure 2. Satisfaction graded by patient 3 months after the 5th
treatment for neck lines and forehead rhydits (0—Unsatisfied;
5— Moderately satisfied, 10—Extremely satisfied). Results obtained
on 20 patients.
Initial stress (K Pascal)
Patient satisfaction rating
10
17
15
13
forehead
11
9
7
5
before
1 month 1 month 3 month
after 3 Tx after 5 Tx after 5 Tx
Figure 4. Initial stress (skin firmness) measured on forehead (20
patients) as a function of time. Before the first treatment,
7.62 3.68 KPa; 1 month after the third treatment, 14.06 7.19 KPa; 1 month after the fifth treatment, 15.36 8.62 KPa; and
3 months after the fifth treatment, 16.68 7.44 KPa. When the final
measurement is compared to the initial one, a statistically significant
improvement is obtained (po0.0002).
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Dermatol Surg 30:6:June 2004
Figure 5. Forehead before treatments.
the third treatment, which was systematically noted 3
months after the last treatment, with some of the
wrinkles becoming smoother and others nearly disappearing (Figures 5–8).
Discussion
This study presents a clinical evaluation of nonablative
remodeling of neck lines and forehead rhytids using a
1.54-mm Er: glass laser. Previous clinical studies on
periorbital and perioral rhytids have demonstrated
that irradiation with this laser can lead to new collagen
formation, dermal thickening, reduction of skin
anisotropy, and clinical improvement with no adverse
effect.1–3
Nonablative remodeling with lasers is achieved
through heating the papillary dermis while providing
epidermal protection. The level of dermal injury in
nonablative techniques is controlled by synchronizing
surface cooling and heating. Heat is generated within
the zone of optical penetration by direct absorption of
Figure 6. Forehead 3 months after five treatments.
laser energy. Heating decreases with tissue depth as
absorption and scattering attenuate the incident beam.
Based on absorption and effective scattering coefficients in the skin, the optical penetration depth can be
determined with the equation8
d ¼ ð3ma ½ma þ ms ð1 gÞÞ1=2
The optical window from 1.2 to 1.8 mm appears to
be well suited for nonablative remodeling as penetration depth within this range is limited to the upper
dermis.9–12 Table 1 displays the absorption and
reduced scattering coefficients of human skin in this
specific window.
Complete reviews of the literature about nonablative remodeling performed with lasers and intense
pulsed lights have been published recently.13–15 Nevertheless, knowledge of remodeling is still limited, with
many studies using poor analytical methods.13 It,
however, seems that patients are truly satisfied
with these procedures both in the short and in the
long term. Most studies present results at 3
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877
Figure 7. Neck before five treatments.
months8,10,12,16–26 or at 6 months’ follow-up.1,3,9,27–30
Very few studies offer long-term follow-up (more than
1 year).2,31,32 A 5-year follow-up involving patients
treated with intense pulsed light on the face, neck, and
chest has been presented by Weiss and colleagues.32
Actinic changes including telangiectasias, mottled
pigmentation, and poikiloderma were evaluated after
the procedure. Ninety percent of the patients were
improved on all these criteria. Nevertheless, this
clinical evaluation was based on a subjective methodology (photo examination and patient self-assessment).
Results from this clinical evaluation on 20 female
patients (ages from 25 to 56 years; mean 45 years) on
neck lines and forehead rhytids show a significant
clinical improvement in visual appearance, skin tone,
and skin texture. Clinical pictures show evident
reduction of rhytids (Figures 5–8). In most cases
wrinkles became smoother with, in some cases,
complete wrinkle disappearance.
This clinical evaluation was combined with the
measurement of skin thickness and mechanical proper-
Figure 8. Neck 3 months after five treatments.
ties. Routinely used in the cosmetic industry, these
techniques give quantified data that can be correlated
with a clinical improvement. Dermal thickness and
skin firmness were particularly studied.
The thickness of the skin changes with age: young
skin gradually gets thicker until about 20, after which
a gradual atrophy of the dermis is observed.33 With
aging skin, it has been demonstrated that this atrophy
reduces the thickness of the dermis.34 Measured by
ultrasound imaging, our study on neck lines and
forehead rhytids shows progressive dermal thickening
on all patients over time. The increase in dermal
thickness was 70 13 mm (po0.001) on the forehead;
it was 110 19 mm (po0.003) on the neck, with a
progressive increase observed after each session. Three
months after the final session, a slight reduction was
observed when compared to the value obtained 1
month after completion of the treatment. This slight
reduction can be expected as a horizontal rearrangement of the new collagen fibers typically occurs in
time.35–37 This observation correlates with previous
studies conducted by us using the same laser.2 There
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DAHAN: REMODELING OF NECK LINES AND FOREHEAD RHYTIDS WITH A LASER
Table 1. Absorption and Scattering Coefficients and Optical
Penetration Depth in Skin as a Function of Wavelength
(Calculation Using Data Provided by Troy and Thennadil40)
Wavelength
(mm)
1.32
1.45
1.54
Absorption
Coefficient
ma (cm 1)
Effective
Scattering
Coefficient
ms 0 (cm 1)
Optical
Penetration
Depth d (mm)
in Skin
1
16
10
14
12
11
1.49
0.27
0.40
are no comparable data in the literature using other
nonablative lasers but histologic studies reported by
several authors using different nonablative lasers have
proved that growth of the upper dermis is due mainly
to an increase in collagen fibers and not to other
components of the matrix.9,22,30,38
The analysis of mechanical properties of the skin
shows a dramatic modification of the mechanical
properties of the skin with 112% increase of the initial
stress. The score increases from 7.62 (usually the value
for female patients of average age 45 years) to 16.68—
a value usually obtained in younger patients.7 This
initial stress gives an average of the initial tension of
the skin and a quantified value of the firmness of the
skin. These measurements are well correlated with the
high level of satisfaction expressed by patients regarding the improvement in skin tone and texture.
It must be emphasized that these results are not due
only to the wavelength, but also to a judicious choice
of the parameters. With the same wavelength, but
using a different machine, not only could Ross and
colleagues8 not achieve remodeling but also obtained
many unwanted side effects (scars, blisters, etc.) when
treating the postauricular area, which is not a sundamaged area. Fluences used ranged from 16 to 146 J/
cm2, 2 to 6 J/cm2 by pulse, and the number of pulses
ranged from 8 to 48. The skin was cooled at 101C
and the spot was 5 mm. The lack of remodeling after
the procedure could be explained by two main facts.
The delay between pulses inside the pulse train was too
short: less than one-half of the one used in Mordon’s
experimental study.39 Fluences were too high, because
the critical efficacy threshold for epidermal damage is
around 60 J/cm2. By emitting in a pulse train mode,
this laser allows to adjust the depth where the thermal
effect should be spatially induced. The experimental
study demonstrates that it is a much better solution
than single-pulse emission39 and that its depth can be
modulated, within limits, by adjusting the cooling
temperature and the number of pulses in the sequence.
In all treatments, a fixed temperature of 151C was
Dermatol Surg 30:6:June 2004
used to cool the epidermis and the depth of the thermal
effect was increased with the number of pulses.
Fluence per pulse was also adapted so the intensity
of the thermal effect induced by the total fluence could
be controlled to avoid reaching the critical temperature leading to cell destruction, the aim being to
stimulate fibroblasts, not destroy them. Although
tempting to physicians who like to have a clinical
end point (redness for instance), this attitude should be
avoided. As this study is proving that remodeling is
efficient without any adverse effect, even after
extensive follow-up, parameters should be kept within
reasonable limits to ensure that total fluence per burst
does not lead to cellular death. This would only lead to
numerous unwanted side effects without increasing
fibroblast stimulation. Thickness of preserved tissue is
greater at the lowest temperature, and the depth of
tissue damage depends on the number of pulses per
burst. According to this principle a different number of
pulses per burst was used depending on the thickness
of the skin in the treated area so as to obtain a thermal
damage at a determined depth of the dermis corresponding to the area responsible for fibroelastosis.
Using the same laser and similar parameters,
Lupton and colleagues3 performed remodeling on 24
patients who had discrete to moderate wrinkles on
perioral and periorbital areas. Fluences ranged from
30 to 40 J/cm2, 10 J/cm2 per pulse. The number of
pulses per burst ranged from 3 to 4. Patients had four
treatments at 1 month intervals. Clinical evaluation
and digital pictures were performed at 1, 3, and 6
months after the last treatment. Samples for histology
were taken just after, at 1 month after, and at 6 months
after the first treatment. A progressive improvement of
skin texture and wrinkles appearance was obtained
after each control. There were no unwanted effects
other than a brief erythema caused by the cooling
device. Biopsies of the last control showed a significant
increase in collagen. These results are very similar to
those obtained in our previous study. The authors
insisted that improvement is slow and occurs over
months. Specific to remodeling, this must be clearly
explained to patients whose expectations may otherwise not be met, potentially leading to a high drop out
rate.
Conclusion
This study demonstrates that irradiation with 1540nm Er:Glass on neck lines and forehead rhytids
provides effective and safe nonablative remodeling of
the skin. Overall great patient satisfaction is confirmed
by clinical pictures and correlated with an increase in
dermal thickness and skin firmness.
Dermatol Surg
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DAHAN: REMODELING OF NECK LINES AND FOREHEAD RHYTIDS WITH A LASER
Acknowledgments The authors thank Quantel Medical
(France) for the loan of the laser and Pascal Servell for careful
reading of the manuscript.
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Commentary
This report describes the use of a 1540-nm Er:Glass laser for
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ablative laser treatments have become immensely popular
because of the ‘‘no-down-time’’ appeal. Patients notice subtle
improvements visually and texturally. Studies on nonablative
lasers are equally popular showing varying degrees of improve-
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DAHAN: REMODELING OF NECK LINES AND FOREHEAD RHYTIDS WITH A LASER
ments seen or unseen to the patients and observers. Recent
studies on nonablative lasers have added more objective
measurements to better document a correlation with the visual
improvement.
In addition to the visual inspections, Dahan et al. used
ultrasound imaging to measure skin thickness at various time
points after the treatment sessions and showed a thickening of
the dermis that was purported to correlate with new collagen
growth and remodeling. Additionally, an echorheometer was
used to measure the mechanical properties that correlate with
skin tone and texture. Again, improvement was observed after
the laser treatment.
Dermatol Surg 30:6:June 2004
The clinical improvement seen from nonablative laser
treatments can be a subtle process. It is therefore reassuring
that objective measurements validate these improvements.
Further studies need to be performed to assess whether these
changes are only temporary or have longer term implications.
Additionally, comparisons between the various nonablative
systems would further enhance our knowledge on the differing
impact of various different wavelengths.
Ken K. Lee, MD
Portland, Oregon