Published online: 15.01.2020
Free full text on www.ijps.org
Overview of lasers
Uddhav A. Patil, Lakshyajit D. Dhami1
LakshyaKiran Cosmetic and Laser Centre, Kolhapur, Maharashtra, 1Vasudhan Arjin Cosmetic and Laser Surgery, Mumbai,
Maharashtra, India
Address for correspondence: Dr. Uddhav A. Patil, LakshyaKiran Therapeutic Lasers and Research Institute Pvt. Ltd., 10-11, Trade Centre,
Station Road, Kolhapur - 416 001, Maharashtra, India. E-mail: kpr_uddhav5@sancharnet.in
aser surgery of skin conditions having cosmetic
implications has revealed the profound psychological
benefits which are unmatched by any other modality
of treatment either with or without a knife. An increasingly
sophisticated understanding of the biophysics of lasertissue interactions has lead to a more efficient utilization
of the present technology on the clinical side and at the
same time is helping the physicists to add more and more
highly selective laser systems in the armamentarium of
aesthetic laser surgeons.
L
This article provides a general overview of lasers in
skin and cosmetology and discusses its current clinical
applications from Plastic Surgeon’s point of view.
M onochromaticity: The luminous waves emitted come
out with the same wavelength and energy. A single
wavelength or a narrow band of wavelengths emitted
allows precise targeting within tissue, while sparing
adjacent structures.
Brilliancy: The light beam emitted is extremely intense
and angularly well centred. The brightness or intensity is
one of the important properties and can be enhanced by
techniques like pulsing and Q-switching where extremely
high peak power can be delivered in nanoseconds.
Coherency: All the photons emitted vibrate in phase
HISTORY
agreement both in space and time. Coherence is a
measure of precision of the waveform. Highly coherent
laser beam can be more precisely focused.
Laser is an acronym for “Light Amplification by Stimulated
Directionality: All the photons travel in Uni direction.
Emission of Radiation.” Stimulated emission was based
on Einstein’s quantum theory of radiation. .[1] The first
laser was produced by Theodore H. Maiman on 7 th July
1960 using ruby as a lasing medium that was stimulated
using high energy flashes of intense light.[2] The Decade
of 1960s will always be remembered in the history of
lasers as more than ten different lasers were invented
using solid, gaseous, semi-conductor as well as liquid
lasing media. The refinement of technology along with
invention of newer lasers has continued till date and will
keep on doing so in the future as well.
Directionality of the laser correlates with the emission
of an extremely narrow beam of light that spreads
slowly. Within the laser apparatus, efficient collimation
of photons into a narrow path results in a divergence
factor of approximately 1 mm for every metre travelled.
Directionality allows the laser beam to be focused on a
very small spot size.
A significant understanding of lasers and light sources is
required for their optimal use. Also a basic understanding
of laser physics is mandatory to carry out an efficient
laser treatment.
LASER CHARACTERISTICS
Laser light is monochromatic, bright, unidirectional and
coherent.
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Terminology and measurements
1. IPL: Intense Pulsed Light where peak optical power
per pulse is up to 20,000 watts achieved with
capacitor banks. All bright light sources are not called
IPL, they are just light sources. Wavelengths emitted
range usually from 400 nm to 1200 nm and the lower
wavelengths can be eliminated by various cut off
filters which usually range from 515 to 755 nm.
2. I2 PL: Second generation Intense Pulsed Light where
wavelengths from 900 to 1200 nm are eliminated.
3. Chromophore: Chromophore is a material, present
either endogenous in the tissues or exogenous i.e.
brought from outside, which absorbs particular
Indian J Plast Surg Supplement 2008 Vol 41
Patil and Dhami
wavelengths depending on its absorption coefficient.
Examples of endogenous chromophores are melanin,
haemoglobin, (oxy haemoglobin, de-oxyhaemoglobin
and meth haemoglobin), water, protein, peptide bonds,
aromatic amino acids, nucleic acid, urocanic acid
and bilirubin. [3] Exogenous compounds like different
colors of tattoo ink also act as chromophores.
4. Parameters: Parameters are the values of wavelength,
fluence (see below), number of pulses, pulse duration,
pulse delay, repetition rate and spot size which
are set on laser or IPL systems to treat a particular
condition.
5. Lasing is the process of treating a lesion or a condition
with lasers or light.
6. Wavelength: The distance between two subsequent
peaks or troughs of a light wave. Usually it is expressed
in nm (nanometre i.e. 10 -9 metres)
7. Hertz (Hz): A unit of frequency equal to one cycle per
second.
8. Frequency (V or f) ∝ (1/ wavelength (Hz) Therefore
shorter the wavelength, higher is the frequency and
longer the wavelength, lower is the frequency.
9. Photon: Photon is an elementary particle responsible
for electromagnetic phenomena. It is the carrier
of electromagnetic radiation of all wavelengths,
including in decreasing order of energy, gamma rays,
X-rays, ultraviolet light, visible light, infrared light,
microwaves, and radio waves. The photon differs from
many other elementary particles, such as the electron
and the quark, in that it has zero rest mass; therefore,
it travels (in a vacuum) at the speed of light.
10. Energy: Each photon carries a ‘quantum’ of energy (E),
whereby: E= hV (h – Planck’s constant) Therefore:
Short wavelength = high frequency = high energy
photons
Long wavelength = low frequency = low energy
photons
Measurements used routinely in laser applications
include wavelength, frequency, energy, fluence, power,
and irradiance.
1. Energy: Energy is measured in joules (J) and is
proportional to the number of photons.
2. Power: Power is the rate of delivery of the energy. It
is measured in watts (W) where 1 W = 1 J/sec.
3. Fluence: Fluence is the energy delivered per unit area.
It is measured in J/cm 2
4. Irradiance: Irradiance is the power per unit area. It is
measured in W/cm 2
Indian J Plast Surg Supplement 2008 Vol 41
LASER TISSUE INTERACTION[3]
Laser beam that encounters skin surface may be reflected,
transmitted, scattered or absorbed at each layer. Once the
laser beam falls on the skin, from this point onwards, we
should think about it not as a light but as a continuous or
pulsed source of photons. Photon as a particle can only
interact with matter by transferring the amount of energy.
Therefore, only absorbed photons can produce tissue
effect. For photon absorption in a tissue, a chromophore
is required. Therefore, our aim is to increase the photon
absorption by reducing its reflectance, scattering and
transmission.
Transmission: If there is no chromophore then all the
photons will pass through the tissue without producing
any effect. This is total transmission. Therefore, selection
of a proper chromophore in or near the target tissue is a
first important step in laser therapy.
Reflection: Reflection occurs at all interfaces of media
through which the laser beam is travelling, such as
optical glass or sapphire tip, air, water jelly and skin
surface. For example, the stratum corneum reflects
approximately 4% to 7% of visible light that encounters
the skin surface. Reflection is minimized by either a firm
contact between the laser head of contact lasers or a
light guide of I2 PL system and skin or by using a layer of
optically transmissible clear jelly between them in case
of IPL systems.. In case of focused and collimated beams,
reflection can be minimized by holding the hand piece
exactly perpendicular to the skin surface.
Scattering: Scattering is due to lack of homogenety in the
skin’s structures, such as molecules, organelles, cells or
larger tissue structures. In the dermis, scattering has been
shown to occur predominantly from inhomogeneities in
structures whose size is of the order of the wavelength
or slightly larger e.g. collagen fibres. It, therefore,
appears to act as a turbid matrix in which scattering
is an approximately inverse function of wavelength
(shorter wavelength, greater scattering). The greater
the scattering, less will be the depth of penetration, and
more possibility of absorption. [4]
In the tissues more scattering occurs when a small spot is
used. In case of large spot, after scattering, photons hit
each other and get recollected and redirect themselves
in the direction of the beam thereby increasing the
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Overview of lasers
depth of penetration. Therefore, larger the spot deeper
is the penetration. However the selection of spot size
also depends on the power generation of the system as
well as on the depth of the chromophore from the skin
surface.
Absorbed photons can produce thermal, mechanical,
or chemical changes in and around the chromophore.
Out of these, thermal changes are most useful, as
in hair reduction, skin rejuvenation and in vascular
lesions. Physical or mechanical tissue changes, known as
photoacoustic changes occur when high energy photons
are delivered in ultra short pulses of nanoseconds. This
is made use of in removing tattoos and clearing certain
pigmented lesions.
Example of light energy causing a chemical reaction is
photosynthesis in plants. The UV irradiation induced
chemical changes in deoxyribonucleic acid (DNA) may be
responsible for cell death and neoplastic transformation.
Selective photothermolysis
In 1983, Anderson and Parrish [5] described the theory
of selective photothermolysis, which revolutionized
laser therapy by explaining a method of producing
localized tissue damage sparing the surrounding tissues.
For understanding this we need to understand certain
terms.
1. Threshold fluence of a tissue is a fluence, which if
equaled or exceeded leads to the tissue destruction.
2. Thermal relaxation time (TRT) is defined as the time
required by an object to cool down to 50% of the
initial temperature achieved.
For tissue damage to ensue a wavelength should be
preferentially absorbed by the chromophore in the target
tissue and not absorbed by the surrounding tissue, it
therefore needs to be delivered in a pulse duration which
is less than or equal to the thermal relaxation time (TRT)
of the target. If delivery time exceeds the TRT then the
target does not get damaged instead the energy dissipates
to the surrounding tissues inflicting injury there. Even
if energy delivery occurs within the TRT limits, the
fluence reaching the target after subtracting reflection
and scattering in the path needs to equal or exceed
the threshold fluence to cause tissue destruction. This
seemingly difficult task can be achieved by manipulating
three variables: wavelength, pulse duration, and fluence.
Wavelength: Wavelength has a dual impact attributable
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to its absorption coefficient in different chromophores
[Figure 1] [6] as well as the depth of penetration from the
skin surface, which roughly increases as the wavelength
increases in the visible and near infra-red spectrum. After
carefully choosing a proper wavelength for a particular
chromophore, the laser surgeon has a difficult task of
delivering maximum number of photons to the target
chromophore before they are snatched by competing
chromophores which are present before the target. By
manipulating the other two variables i.e. pulse duration
and fluence, this can be done effectively. Not only this, but
by choosing proper pulse duration a smaller or a larger
target having the same chromophore can be selected.
Pulse duration: Selection of pulse duration is mainly guided
by the TRT, which in itself is related to the size of the
target. As a general rule, larger the chromophore, longer
is the TRT as large objects take long time to cool. More
difficulty is encountered while lasing the smaller targets
as the short pulse width required makes the epidermis full
of melanin more vulnerable (TRT 10 ms). This is achieved
by dividing this short pulse into still shorter rations of
pulses which are delivered in succession. This form of
energy delivery is called multiple synchronized pulsing.
M ultiple Synchronized Pulsing: [Figure 2] Even though
the epidermis is a strong competing chromophore for
smaller targets, it can be spared as long as the TRT of
the target is longer than that of epidermis. Longer TRT
means the target takes longer time to cool to 50%of the
temperature achieved. By multiple synchronized pulsing,
which are usually two to three and maximum five pulses,
with delays in between, both the target and epidermis are
heated by the first pulse just within the threshold limit of
the epidermis, therefore the epidermis is not damaged.
After the first pulse there is a delay, during which both
epidermis and target start cooling, but as the target cools
slowly at the end of the delay it still retains some heat
while the epidermis has cooled down completely. During
the second pulse and the delay thereafter, the same
sequence repeats but now the target gets heated to a
higher level as it is starting from an elevated base line.
This pulsing is repeated till such time as the temperature
in the target at the end of last pulse exceeds its threshold
limit. [7]
CLINICAL APPLICATIONS
The present clinical applications in skin conditions and
cosmetology which most concern a plastic surgeon can
Indian J Plast Surg Supplement 2008 Vol 41
Patil and Dhami
be
1.
2.
3.
4.
grossly divided into following five categories:
Unwanted hair
Vascular lesions, acne and scars
Pigmented lesions and tattoos
Skin rejuvenation by ablative and non ablative laser
resurfacing
5. Leg veins and varicose veins
Unwanted hair
During the last decade permanent reduction of unwanted
hair by lasers and light sources has been established as
a quick, safe and sure method of choice over all earlier
modalities of hair removal which were temporary. For
permanent reduction the hair root should be destroyed.
The term hair root refers to hair within the hair follicle.
Here it will be appropriate to quickly review the relevant
anatomy.
Hair follicle anatomy
Hair follicle is divided into three units:
Infundibulum includes the region from the hair follicle
orifice to the sebaceous duct entrance.
Ist hmus encompasses the region between the entrance of
the sebaceous duct and the attachment of the arrector
pili muscle.
Inferior segment is the region from the insertion of the
arrector pili muscle to the base of the follicle and includes
the hair follicle bulge and the bulb.
The hair follicle bulge is the extended lower portion of
the hair follicle between the insertion of the arrector
pili muscle to the hair bulb. The bulge has more or less
constant distance of 1.5 mm from the skin surface.
The hair follicle bulb is the lowest portion of the hair
follicle and is composed of matrix cells, interspersed by
melanocytes, which produce hair. The distance of the bulb
from the skin surface varies with the different stages of
hair growth. It is shallowest at early anagen and deepest
at late anagen stage. In anagen itself coarser the hair,
deeper will be the follicle [Table 1].
Melanin of hair root is the chromophore which absorbs
photons and gets heated. Melanin has a wide and gradually
sloping down absorption coefficient curve spanning
from ultraviolet to infrared spectra giving a wide choice
of wavelengths to chose from [Figure 1]. This liberty of
Indian J Plast Surg Supplement 2008 Vol 41
choosing wavelengths is restricted by the presence of the
same melanin as a competing chromophore in variable
quantities in the epidermis of different skin types. An ideal
target is an extra coarse, dark black hair root in anagen
growth phase on a lighter skin type. The most difficult
is a fine, lightly pigmented hair of a darker skin type.
In any case, if the target is lighter than the epidermis,
no available laser can act on it at present. However,
attempts are underway to enhance the absorbability of
such lighter targets by incorporating external pigment in
them. Meladine TM[8] is one such exogenous chromophore
enhancer.
Hair ro o t is o ne example where t arget and chro mo pho re
are no t exact ly t he same. Melanin co nt ent o f t he hair bulb
and bulge is t he chro mo pho re which abso rbs pho t o ns
and get s heat ed. The t arget is fo llicular epit helium which
is at so me dist ance surro unding t he bulb. Therefo re,
t he bulb needs t o be heat ed lo ng eno ugh t o allo w
sufficient heat t o get co nduct ed t o t he t arget . Tho ugh
t he chro mo pho re in case o f ext ra co arse, m edium and
fine hairs is melanin, t hey can no t be lased wit h t he
same paramet ers as t he size o f t he chro mo pho re in t he
bulb and bulge is no t t he same in t hree. The ro o t o f
an ext ra co arse hair will never get dest ro yed, ho wever
high t he energy, if yo u use a sho rt er pulse. Yo u are just
no t allo wing sufficient t ime fo r a larger chro mo pho re
t o get sufficient ly heat ed and dissipat e it s heat t o t he
surro unding t arget . Ext ra co arse hair needs lo nger pulse
durat io n t han medium, and fine hair needs t he sho rt est .
Therefo re, t he pulse durat io n sho uld be primarily guided
by t he size o f t he chro mo pho re and o nly seco ndarily by
t he co mpet ing chro mo pho re. Epidermal melanin po ses
as a co mpet ing chro mo pho re in case o f all lasers in
t he visible and infra red spect rum o f light [Figure 1],
t herefo re it will be wo rt h t o co nsider a classificat io n o f
skin based o n epidermal melanin co ncent rat io n and it s
respo nse t o sun [Table 2].
Table 1: Corresponding hair shaft diameter with anagen hair
follicle depth. (Exceptions exist)
Quality of the
hair
Shaft diameter
microns
Very Þne
Fine
Medium
Coarse
Very coarse
Extra coarse
Super coarse
< 25
25-51
51-76
76-102
102-127
127-152
> 152
Anagen follicle depth
Millimeters from skin
surface
<1
1-2
2-3
3-4
4-5
5
5
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Overview of lasers
3 rd peak of the absorption curve of haemoglobin and 450
micro second pulse duration which was less than the TRT
of the smaller vessels of PWS. Later on it was replaced
by yellow light at 585 nm and 595 nm having deeper
penetration and giving better results. PDL treatment is
the method of choice for most PWS in children [Figure
3]. The IPL sources with a cut off filter of 590 nm are also
quite effective and are being routinely used for a variety
of vascular lesions including PWS [Figure 4].
Shorter wavelengths like Ruby 694 nm and Alexandrite
755 nm were the first ones to be used for hair reduction.
Though they have higher affinity to melanin, they can
not penetrate deeply in the skin. In darker skin types V
and VI they led to unacceptable rate of complications like
epidermal burns and post treatment hyper pigmentation
due to strong competing epidermal melanin. In contrast
longer wavelengths like Diode 800 nm and Nd:YAG 1064
nm though having lesser affinity to melanin as compared
to shorter ones are found to be more effective due to
deeper penetration to the deeply placed hair follicles
which at times are 3 to 4 mm deeper. At present both
these wavelengths are found effective for hair reduction in
darker skin types. Therefore the reach of the wavelength to
the target is also an important consideration. Remember,
photons have to first reach the target to get absorbed.
By extending the principles of selective photothermolysis
and by making use of multiple synchronized pulsing, the
laser surgeon is now able to selectively target a larger
or a smaller vessel in the same lesion having the same
common chromophore haemoglobin. The only limiting
factor in laser treatment of vascular lesions at present
is the reach of the lesion (i.e. its depth from the skin
surface. Currently a wavelength of 1064 nm can reach a
maximum of 8 mm) and the flow in the lesion (only slow
flow lesions can retain the generated heat long enough
for the tissue destruction).
Vascular lesions, acne and scars
In vascular conditions, haemoglobin is the chromophore
and the vessel wall is the target. Water contained in
the cells of the vessel wall also acts as an additional
chromophore. Haemoglobin has absorption coefficient
curve with peaks at 418 nm, 524 nm, 577 nm and again
at 1064 nm [Figure 1]. At the first and second peaks the
melanin absorption is also very high and therefore these
wavelengths can not be used. However, the spectrum
between 580 nm and 590 nm is useful clinically. Pulsed
dye laser (PDL) with a wavelength of 595 nm is at present
considered as a gold standard for vascular lesions.
Some advanced systems have Dynamic Cooling Device
(DCDTM). [10] cooling to safeguard the epidermis. Here a
cryogen spray falls on the skin milliseconds before the
laser pulse and cools the epidermis by rapid evaporation
thus protecting it.
Haemangioma
The commonly used 590 and 595 nm wavelengths, being
shorter, can act only on superficial lesions up to 1.2
mm depth. PWS, superficial haemangiomas and other
superficial vascular lesions are treated by these. For
deeper vascular lesions like deep haemangiomas, 1064
nm wavelength is used [Figure 5].
Acne
Non intense Light Heat Energy (LHE) sources, IPLs and
Lasers are playing an important role in multi-modality
approach to management of acne and at present their
role is three fold: in active acne with haemoglobin and
water as chromophores, [Figure 6] in acne induced
pigmentation and in post acne scarring. Diode 1450 nm
with water absorption is found effective in inflammatory
acne. This as well as Erbium: glass 1540 nm Lasers are
found promising in contouring atrophic acne scars.
Port wine stains (PW S)
Flash lamp pumped dye laser was the first example
of a laser which was specifically built to treat PWS
after understanding the principles of selective
photothermolysis having 577 nm wavelength to match
Table 2: Fitzpatrick’s skin photo types[9]
Skin type
Type I
Type II
Type III
Type IV
Type V
Type VI
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Skin colour
White
White
White
Moderate brown
Dark brown
Black
On exposure to sun
Burns
Always
Usually
Sometimes
Rarely
Very rarely
Never
Lancer ethnicity scale
Tans
Never
With difÞculty
Averagely
Easily
Easily
Very easily
Caucasian
Caucasian
Caucasian
Asian, mid eastern
Indian
Black
Indian J Plast Surg Supplement 2008 Vol 41
Patil and Dhami
Scars
In scars role of lasers and IPL systems spans from
fibroblast modulation in fresh scars, clearing scar
pigment, removing traumatic tattoos to remodelling of
collagen in hypertrophic scars [Figure 7] and even older
scars. Fresh scars are hypervascular, haemoglobin is the
abundant chromophore and fibroblast is the target. Fresh
scars can be made inconspicuous. PDLs, IPLs with 590
cut off filter have shown good results [Figure 8]. Recently
introduced Er: Glass 1540 nm fractional lasers also have
shown promising results.
Pigmented lesions and tattoos
Figure 1: The absorption of various chromophores as a function of
wavelength. [6]
As melanin absorbs light at a wide range of wavelengths,
from 250 nm to 1200 nm [Figure 1] almost any Laser with
sufficient power causing thermal denaturation can be used
to remove benign pigmented lesions of the epidermis.
In dermal pigmented lesions the target chromophore is
intracellular pigment melanosomes or tattoo particles.
To make such sub-micrometer particles absorb photons,
the energy delivery needs to be in nanoseconds (TRT) as
compared to milliseconds for hair root and microseconds
for capillaries. This has been made possible by a technique
invented in 1962 called quality switching or Q-switching.
Normally in a lasing chamber, once population inversion
occurs i.e. the number of stimulated photons exceeds
resting photons, the laser beam emerges through the
partially reflective mirror. In Q-switching, the energy or
number of stimulated photons is deliberately allowed
to build up to a higher level by blocking the partially
reflective mirror with a Pockels cell. Pockels cell contains
Figure 2: Multiple synchronized sequential pulsing.[7]
Indian J Plast Surg Supplement 2008 Vol 41
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Overview of lasers
laminar opaque crystals which become transparent only
when an electric current is applied for a few nanoseconds
controlled by an electronic switch. When transparent, the
built up photons get released just for a few nanoseconds
and blocked again to get rebuilt up. These ultra short
high energy bursts of pulses lead to mechanical photo
acoustic damage in the target cells. Q-switching is
available with Ruby 694 nm, Alexandrite 755 nm, Nd:YAG
1064 nm and frequency doubled FD Nd:YAG 532 nm (i.e.
in the path of QS Nd:YAG 1064nm beam, a KTP crystal is
brought which changes the frequency to double so the
1064 nm wavelength becomes half i.e. 532.) KTP laser is
also available as a non QS laser with 532 nm wavelength.
This is an example of a laser beam being used as a source
of energy (instead of a flash lamp ) to stimulate another
lasing medium. The rate of heating and rapid material
expansion with Q-switched Lasers can be so severe
that tissues are torn apart by shock waves, cavitation
or rapid thermal expansion. The immediate effect on
the pigmented skin is whitening, due to melanosome
rupture and pyrolysis leading to formation of gas bubbles
that scatter light. Immediate whitening offers a clinically
useful treatment end point.
Selective photothermolysis with various Lasers is highly
useful for epidermal and dermal pigmented lesions in
which cellular pigmentation is the cause, however lasers
and IPLs have variable usefulness for dermal melasma
and post inflammatory hyper pigmentation because
the etiological factors may still persist and lead to
recurrence.
Treatment
The approach to the treatment depends on location
of pigment (epidermal, dermal or mixed), the way it is
packaged (intracellular or extracellular) and the nature
of pigment (melanin or tattoo particle). Continuous wave
lasers like CO2 (10,600 nm) or Er-YAG (2940 nm) with
water as a target chromophore in epidermis can be used
for removing the superficial pigmented skin, especially
seborrheic keratosis and ‘Q-switched resistant’ Café-AuLait macules. But the non selective thermal injury may
lead to some erythema and possible pigmentary and
textural changes. In many pigmented lesions however,
the melanosomes and melanocytes are clustered so
compactly that they act as a larger body of chromophore.
In this situation, melanin specific wavelengths even in
millisecond domain also lead to lesion clearance. These
long pulsed lasers are only suitable to treat nevocellular
Figure 3: PWS before and after 6 treatments with PDL 595 nm
Figure 4: PWS before and after 10 treatments of IPL with 590 nm Þlter
Figure 5: Haemangioma in a Þve month old baby in rapid proliferative phase
before and 1 year after 5 treatments with Nd:YAG 1064 nm. Note undamaged
eyebrow and eyelashes, example of chromophore speciÞcity. Eye was protected
by a special metal corneal shield.[11]
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Figure 6: Severe pustular acne before and after 2 IPL treatments (590 Þlter) as
a part of multimodality approach
Indian J Plast Surg Supplement 2008 Vol 41
Patil and Dhami
Figure 8: (A) Extensive windshield injury of face. (B) Result after primary plastic
surgical repair. (C) Result after 4 IPL treatments (590 Þlter) at monthly interval
Figure 7: Post traumatic hypertrophic scar before and after 1 PDL and 4 IPL
treatments (590 Þlter.)
Figure 9: Congenital melanocytic nevus before and after 8 IPL treatments. First
6 treatments with 645 Þlter for deeper pigment and last 2 with 615 Þlter for
superÞcial pigment. Eye was protected by a special metal corneal shield.[11]
Figure 10: Melasma before and after 2 IPL treatments with 645 Þlter. QS
Nd:YAG 1064 nm has cleared residual forehead tattoo around a punch graft in
one treatment and has signiÞcantly lightened the dark tattoo over chin, freckles
and moles with two treatments
Figure 11: Nevus of Ota before and after Q-Switched Nd:YAG 1064 nm laser
treatments. Please note the complete clearance of the pigment without any
residual textural skin change.
nevi while IPL (500 nm to 1200 nm) treats photo damaged
pigmentations like solar lentigines, dyschromia and
melasma [Figures 9,10].
The Q-Switched Lasers (532 nm FD 694 nm Ruby, 755
nm Alexandrite or 1064 nm Nd-YAG) with their high peak
power and pulse width in nano second range are best
suited to treat various epidermal, junctional, mixed and
dermal lesions The Q-switched Nd-YAG is an ideal choice
to treat dermal pigment as in nevus of Ota and in darker
skin types, as it reduces the risk of epidermal injury and
pigmentary alterations. The pigment clearance may be
Indian J Plast Surg Supplement 2008 Vol 41
Figure 12: Multicolored tattoo treated with 4 simultaneous treatments with
Q-Switched 1064 nm (for black and green) and 532 nm (for red). Small
hypertrophic scar is pre-existing
expected to be near total [Figure 11]. In case of tattoos
however, no other laser technique is found to be more
effective than Q-switching. In a multicolored tattoo for
black ink QS 1064 nm, QS 755 nm and QS 694 nm are
excellent. For red ink FDQS 532 nm is excellent. For
green ink QS 755 nm, QS 694 nm and QS 1064 nm are
found to work in that order. [Figure 12]. In India most
commonly done tattoos are amateur and religious using
carbon which clears very well with 1064 nm. [Figure 13]
Treatment pearls
Local anaesthetic cream is applied 1 hour before
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Overview of lasers
treatment to reduce pain and discomfort. The desired
tissue response with Q-switched Lasers is immediate
whitening of treated area and none or minimal pin point
bleeding. It is best to use largest spot size with optimum
power to prevent epidermal damage. Post treatment care
consists of antibiotic cream with or without steroid for
a few days, avoidance of sun exposure with use of sun
block creams and bleaching creams at night to prevent
laser induced hyper pigmentation. Multiple treatment
sessions are preferred at 6 weeks or longer interval with
higher fluence for subsequent treatments.
Skin rejuvenation by ablative and non ablative
laser resurfacing
Resurfacing Laser techniques were developed for their
use in Tissue Tightening for wrinkles and rhytides,
Skin Lightening for superficial sun damage dyschromia,
lentigines or actinic keratosis and Skin Leveling for
atrophic acne or chicken pox scars.
Ablative resurfacing
Ablative resurfacing with CO2 laser (10,600 nm) was the
only option during mid 1990s, with either continuous
wave or ultra short pulse mode, with or without a scanner.
These lasers proved very effective in the Plastic Surgeon’s
armamentarium, but were found to have significant side
effects, especially in inexperienced hands. Prolonged
erythema, hyper pigmentation, contact sensitivity to
topical products, infection, prolonged hypo pigmentation
and deep scarring were main concern.
stronger water absorption and reduced deeper thermal
damage came as an advancement. But though Er:YAG
laser was very good for skin lightening and levelling,
the tissue tightening effect was much less than with
CO2 . Increasing the pulse width increased the residual
thermal damage providing additional benefit but also
increased side effects. The next development came as a
laser that combined Erbium with CO2. Erbium provided
pure ablation, while CO2 allowed heat deposition for skin
tightening. Use of topical anaesthetics, which hydrated
the skin also helped minimise side effects. Despite all
these advances, ablative lasers lead to significant down
time of few weeks to months. The common side effects
seen often are erythema, oedema, infection, flare up of
acne, hyper pigmentation, relative hypo pigmentation
and scarring. The true contraindications are history of
vitiligo, scleroderma, darker skin patients, and unrealistic
expectations.
Ablative laser resurfacing leads to dramatic improvement
in the overall quality of skin. The gains can be up to 50%or
more, including reduction of wrinkles, levelling of deep
scars and vaporisation of superficial skin lesions [Figure
14]. Unacceptable down time of this procedure led to
the development of a promising non-ablative resurfacing
technique, which is now in the forefront.
To decrease these side effects Er:YAG (2940 nm) laser with
Figure 13: Forehead tattoo cleared with 3 sittings of Q-Switched Nd:YAG 1064
nm. (A) After 1st Treatment (B) After 2nd Treatment (C) After 3rd Treatment
Figure 14: (A) Small pox scars (B) After combined derm abrasion and Er:YAG
2940 nm laser resurfacing in a single sitting
Figure 15: Spread and Atrophic ARSTL scar dramatically improved with
Matisse TM[12] Fractional 1540 nm Erbium: glass laser non-ablative resurfacing
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Figure 16: Varicose veins before and after EndoVenous Laser ablation with
Diode 980 nm
Indian J Plast Surg Supplement 2008 Vol 41
Patil and Dhami
Non ablative laser resurfacing
Currently the devices which are available in this field
are either with a vascular target or the ones that target
water in the dermis. The first group includes pulsed dye
lasers (PDL) and intense pulsed light (IPL) devices, which
initiates a cascade of events by controlled wounding of
the dermal micro -vasculature. The second group includes
mid infra red lasers that target water in the dermis to
effect dermal heat deposition. This group includes 1320
nm Nd:YAG, 1450 nm Diode and 1540 nm Erbium: glass
lasers.
The main advantage of non ablative laser rejuvenation
is lack of any downtime for the patients. The devices
that target dermal vasculature will help minimise
telangiectasias, diffuse erythema or rosacea. Devices
which also target melanin like an IPL can also treat
lentigines, melasma, poikiloderma, dyschromia and other
non specific hyper-pigmentation.
Non ablative resurfacing is best for patients with fine
lines, though multiple treatment sessions are usually
necessary. The degree of wrinkle reduction may not
be as dramatic as seen with ablative lasers, so patient
dissatisfaction can be an issue.
specific concerns. If the vascular element is the main
concern then PDL or an IPL with 590 nm filter would
be most suitable. If pigment disorder is the main issue
then IPL with 645 nm filter or near infra red laser of
1064 nm Nd:YAG would provide the best improvement.
The mid infra red lasers induce changes such as vascular
damage, apoptosis, water vaporisation in the dermis and
oedema with imperceptible wounding, which then leads
to a cascade of inflammatory processes and subsequent
neo -collagenesis. The laser beam in effect, penetrates
up to a depth of 2 mm (papillary dermis), resulting into
reduction of rhytides. The different wavelengths of 1320,
1450 and 1540 nm are all often used interchangeably
with similar efficacy, though 1450 nm Diode and 1540
Erbium: glass Lasers are superior in the recontouring of
atrophic scars [Figure 15] and treatment of inflammatory
sebaceous glands. The field of non ablative resurfacing
has expanded dramatically over last 10 years, while the
ablative laser procedures have remained stagnant during
this period.
The efficacy of this laser has been demonstrated by
histological evidence, photography and clinical satisfaction
with tighter, firmer and more toned skin. This occurs as a
result of increase in the number of fibroblasts, increased
The wide array of non ablative rejuvenation lasers allow
us to individualise treatment based on the patient’s
Figure 17: (A) Burns after 2nd HR treatment by IPL even with the longest 755
Þlter in a dark skin type. Photograph on 3rd day. This was a result of neglecting a
warning in the form of a few very superÞcial brownish marks after 1st treatment
with the same Þlter. In such a threshold situation, subsequent ßuence should
be decreased. Here it was rather increased by just 2 J/cm2 (B) Two months
later hyper pigmentation has persisted. This acts as a hindrance to further
treatments
Figure 19: (A) Haemangioma over left cheek. (B) Hyper pigmentation following
5 Nd:YAG 1064 nm laser treatments. A single treatment with Q-Switched
Nd:YAG overcame parental anxiety. (C) Pigment clearing after 2 months
Indian J Plast Surg Supplement 2008 Vol 41
Figure 18: Purpuric spots after PDL 595 nm treatment of PWS. Usually they
clear in a 5 to 7 days period
Figure 20: (A) Congenital Pigmented Nevus. Greenish hue indicates more
deeper pigment (B) Clearing well with QS Nd:YAG 1064 nm laser (3 treatments).
(C) Hypo-pigmentation appeared after 7th treatment (D) Mottling increased with
subsequent treatments and has persisted 3½ months after 12th treatment
S110
Overview of lasers
collagen deposition and normalisation of papillary
dermis. The side effects commonly seen are transient
pain, oedema and erythema. Pigmentary alteration,
blister formation and scarring are very rare.
Fractional resurfacing
Recently a new technology has evolved, which allows
ablative resurfacing of the skin but only on a small
fraction of the skin at a microscopic level. The area
treated with each pass is not more than 10% of the total
surface area. The wavelength used is 1540 nm Erbium:
glass with either a scanning device (Fraxel) or an array of
micro lenses (Matisse TM [12]).
Fractional Laser Resurfacing delivers light in an array
of high precision micro beams. These micro beams
create narrow, deep columns of tissue coagulation that
penetrate well below the epidermis and into the dermis,
while sparing the tissue surrounding the columns from
damage. The coagulated tissue within the columns
initiates a natural healing process that accelerates the
formation of new, healthy tissue. Coagulated cellular
debris is expelled as the skin is resurfaced.
With the fractional Matisse laser there are 1000 micro
spots, in one sq. cm area with each spot diameter
of approximately 100 to 125 microns. The depth of
penetration of Laser energy is approximately 600 microns
to 1 mm. (up to papillary dermis) or more.
Unlike with selective photothermolysis, where the
whole of the selected target area is damaged “Fractional
Photothermolysis” seeks to only damage certain zones
within the selected target area, (producing tiny dot, or
pixel-like treated areas on the skin), leaving the other zones
within it perfectly intact; hence only causing fractional
damage through the heat of the light source. This allows
the skin to heal much faster, than if the whole area was
treated, as the ‘healthy’ untreated tissue surrounding the
treated zones helps to fill in the damaged area with new
cells very quickly.
Fractional Photothermolysis or Fractional Laser Skin
Resurfacing can therefore be compared to the precise
alteration of digital photographs that we are able to do
nowadays; pixel by pixel.
The concept of this fractional laser technology can be
applied with either ablative laser resurfacing or nonablative laser skin rejuvenation, using the various different
wavelengths of lasers available.
S111
This fractional approach (ablative and non-ablative) claims
to achieve comparable skin improvements as obtained
with conventional ablative laser resurfacing with an
Er:YAG or CO2 laser, (depending on depth and severity
of wrinkles), but without the associated side effects or
downtime; i.e. you get the results of an ablative laser but
with the downtime of a non-ablative laser.
Optimal improvement after fractional treatment is usually
visible in about 2 - 3 months as the collagen remodelling
and skin tightening continues. The longevity of results are
comparable to ablative laser resurfacing and as always, is
dependent on the future ageing, effects of gravity and
sun exposure.
Fractional photothermolysis is used for the treatment
known as skin rejuvenation or skin resurfacing. This
includes the reduction and possible removal of fine lines
and wrinkles, improvement of deeper wrinkles, repair
of sun damaged skin on the face, neck, shoulders and
hands, the reduction of age spots and blemishes, acne
scars and hyper-pigmentation, melasma (areas of darker
pigment or brown patches in the skin), telangiectasias
and acne rosacea.
Most patients will be able to return to work
immediately following this type of procedure.
Due to the way the laser treats the skin, it remains relatively
strong, therefore any redness can be camouflaged with
make-up straight away without any ill effects; and men
are also able to shave almost immediately after the
treatment.
Repeat procedures
Unlike with ablative laser resurfacing, where one treatment
is usually enough; multiple treatment sessions are required
with fractional resurfacing to obtain optimal results.
The clinical studies carried out suggest that generally 4-6
treatments spaced about 7 to 21 days apart produce a
gradual remodelling of the skin, until complete healing
occurs; when old tissue is replaced with fresh collagen
and elastin filled tissue. One can expect an overall
improvement in the range of 40 to 50%. The number of
treatment sessions required depends upon the individual
patient and the condition undergoing treatment.
Adverse effects / Complications
Erythema and oedema is common and resolves within
few hours or a day or two. Pigmentary changes either
hypo or hyper pigmentation may be visible after few days
Indian J Plast Surg Supplement 2008 Vol 41
Patil and Dhami
but usually resolves in 3 to 6 months.
Superficial burn or blister may rarely occur, and can be
minimised by careful technique and adherence to the
proper protocols
Leg veins and varicose veins
De-oxyhaemoglobin has almost similar absorption curve
as oxy-haemoglobin. The thread veins and some of the
smaller veins which are dilated up to 5 mm can be treated
with deeply penetrating Nd:YAG 1064 nm
For varicose veins per say no external laser is able to deliver
sufficient energy and that too uniformly circumferentially.
This drawback was overcome with endo -luminal delivery
of laser energy with an optical fiber. These are called as
endovenous procedures and both radio frequency (RF)
and lasers are being used as energy sources. The entire
procedure is done under color doppler guidance. In RF a
tiny catheter with five pronged tip is introduced in the
vein. The four prongs are RF electrodes which open up like
petals of a flower and come in contact with the vein wall.
The central one is a thermocouple which continuously
monitors the temperature and gives a feedback. The RF
energy is directly delivered to the vein wall as the catheter
is very slowly withdrawn. This causes vein wall damage
and its immediate closure.
In endovenous lasers initially Diode wavelengths like
808 nm, 810 nm and 840 nm were used. Now Diode
980 nm is being used and recently Nd: YAG 1320 nm is
introduced. The Diode has absorption in blood while
the latter is claimed to have more absorption in water
contained in the cells of the vein wall causing it’s closure.
Both the RF and lasers have a definite learning curve with
ease of it leaning towards lasers than the RF, because of its
comparatively complicated gadgetry as compared to the
simple 600 micron fiber of the lasers. In all endovenous
procedures the GSV closure rate is around 90 to 95%
[Figure 16].
Side effects and complications
Therapeutic window
Usually every laser and light source has a therapeutic
window, narrow or wide for a particular lesion or condition.
As a rule of thumb, fluence in the therapeutic range is
called as optimal fluence which gives a predictable clinical
response and outcome. Sub optimal fluences are either
non effective or at times have stimulating action while
more than optimal fluences are clinically damaging.
Indian J Plast Surg Supplement 2008 Vol 41
Laser treated skin requires special care, regardless of
the laser used or the lesion treated. As different lasers
produce various skin responses, different post treatment
regimens are required. Prior to treatment, sun exposure,
tanning, retinoids and photo sensitizing drugs increase
the chances of adverse effects and are contraindicated.
After treatment the skin needs to be protected from heat,
sun exposure, handling and infection. Laser treated skin
generally tends to become drier and needs soothing and
moisturizing lotions, creams or gels of aloe vera. It is a
good policy to educate the clients on UV effects on skin
and make them routinely use sun blocks with a minimum
of 30 SPF (Sun Protecting Factor) till the last laser session.
A habit cultivated will certainly help them in proper skin
care.
Complications: In laser treatment complications can be
divided into immediate complications, late complications
and sequelae. Immediate complications occur either
immediately or within a few minutes or hours of laser
treatment. These are usually related to excess fluence,
occasionally related to improper technique and rarely
related to an accident. Excess fluence leads to epidermal
erythema, superficial burn or deep dermal burn with
incident scarring depending on the extent of injury and
pigmentary changes. It can be prevented or minimised
by proper patient and lesion selection, proper parameter
selection, test shots, stepping down on fluence during
summer or when tanning is suspected, effective pre,
intra and post laser cooling of the epidermis. However,
in darker skin types this may not be evident immediately
and therefore a test may be necessary.
Hair removal: In case of laser hair removal, particularly
if plucking was practiced for a long time, folliculitis can
occur. Other side effects are in the form of superficial
burns either due to excess energy or energy intolerance.
Erythema is most usual and transient but can remain for a
few hours and occasionally for a day. Epidermal burns are
more common over bony areas and are due to bouncing
of the laser energy leading to coffee coloured crusting
which usually clears within a day or two but is the cause of
lot of anxiety to clients. Transient hyperpigmentation can
ensue with more severe burns [Figure 17]. Usually it clears
on its own but becomes a hindrance for the next laser
session, therefore de-pigmenting creams are prescribed.
Hypo -pigmentation is rare. Pigmentary changes are more
seen in darker skin types. Paradoxical stimulation of more
number of hair follicles in the area being treated or even
in the adjacent areas which start growing longer and
S112
Overview of lasers
coarser hairs is a known entity. The possible explanations
offered are, stimulating effect of the sub-optimal energy
in the treatment area, scattering of the laser energy in
adjacent dermis again acting by above mechanism and
may be production and diffusion in the adjacent areas of
some chemical mediators yet unknown to us. Whatever
may be the cause, this complication apparently frightens
the patient who needs assurance and confidence from
the surgeon: “Its good that they are growing. More of
them grow, more we will be able to destroy permanently
in next sittings”.
Vascular: Severe oedema and swelling, purpura, blisters,
infection, crusting, hyper and hypo pigmentation and
scarring can occur. In case of lesions like PWS, purpura
and dry crusting are unavoidable [Figure 18]. Antiseptic
creams should be used in the post laser period. Hyper
pigmentation and hypo pigmentations can occur, both
are temporary and do not need active treatment except
in very anxious patients [Figure 19]. Very rarely it can be
permanent and a mention of it should be made in the
informed consent form.
Dr. Leo n Go ldman, MD, is apt ly called t he fat her o f laser
medicine. Immediat ely aft er invent io n o f ruby laser
in 1960 he used it fo r t reat ing a variet y o f pigment ed
lesio ns and explo red it s effect s o n no rmal pigment ed
skin and in 1963 published first ever scient ific art icle
devo t ed t o t he subject o f laser-skin int eract io ns and t he
use o f laser in medicine. [13] The ball was set ro lling. Since
t hen physicist s and physicians all o ver t he glo be have
wo rked hand in hand and have bro ught laser medicine
and surger y t o t he present st age o f glo r y. Unlike o t her
no n-medical fields here in medicine, lasers may st ill
co nt inue t o act as an ext ensio n o f t he human senses.
But who can predict abo ut t echno lo gy advancement s?
There may be a t ime in fut ure, when t his ‘human’ fact o r
beco mes meagre befo re t he giant t echno lo gy. And even
if it happens, ho w wo uld it mat t er? Ult imat ely, is it no t
t he same human sense which has creat ed t he t echno lo gy
and will co nt inue t o refine it ? Whet her t he t echnique o r
t he t echno lo gy, as lo ng as it is used t o alleviat e human
suffering, t he jo y in t he mind using it sho uld remain t he
same.
Pigmeted areas: As t he t herapeut ic windo w narro ws
REFERENCES
in pigment ed lesions, chances of severe burns, hyper
pigmentation and hypo pigmentation are more. Proper
selection of the technology like Q-switching and strict
adherence to the treatment and parameter protocols
plays a very important role in their prevention. With the
best of the above things, please remember that there is
a vast difference between treating a pigmented lesion in
lighter skin types and the similar lesion in darker skin type
[Figure 20]. A safe policy is to start with the parameters
at the bottom of the therapeutic window and make
subtle increments only if there is no favourable response
or the response is static. Protection from sun and depigmenting regimens acquire even more importance in
these situations.
EPILOGUE
Forty eight years are like a dot on the time scale of
human evolution. Lasers are just that young. Looking
at the different aspects of human life and the world as
a community, the various positions and fields which
lasers are occupying today are not less than miraculous.
Medicine is no exception to this. Albeit slower but
with the same miraculous results, laser technology has
doubtlessly created a definite position of importance in
therapeutic surgery and medicine.
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