Use of The Laser in Facial Plastic Surgery

Mr Mike G Dilkes MS, FRCSEd, FRCS, FRCS(ORL-HNS).

Consultant Ear Nose and Throat Surgeon

St. Bartholomew’s Hospital, London EC1Y 0DT, UK.

Chapters

1) History

2) Physics

3) Lasers used in Facial Plastics

4) Clinical areas in Facial Plastics where the laser is effective.

5) Pigmentation problems

6) Safety

7) References

1) History

Light has been used as a therapeutic tool for the skin since the

Finsen lamp was invented in 1899, when it was used initially for Lupus

Vulgaris. In 1901 an ultraviolet lamp was used to treat Rickets, and

scar tissue, followed by PUVA treatment for Psoriasis in 1925. It

was therefore natural that skin became the first area where lasers

were used.

Lasers were first used on the skin soon after Maiman’s breakthrough at

Massachusetts Institue of Technology in 1960(1), when the Ruby laser

became the first laser ever produced. Leon Goldman was a dermatologist

in Cincinnati, and he heard early on about Maiman’s work. He had the

vision to set up a biomedical laser laboratory at the University of

Cincinnati in 1961. At the time the Ruby laser was the only system

available, and although good results were seen on a variety of skin

conditions, there was too much scarring found to establish this as a

mainstay of skin treatment(2). In 1964 the Carbon Dioxide laser,

highly absorbed by water, was made available, and this allowed tissue

such as skin to be cut in a bloodless manner. The same year the Argon

laser also appeared, and this was preferentially absorbed by

haemoglobin, leading to work on port wine stains and other skin

vascular lesions. At the same time this laser was also developed by

Ophthalmic surgeons to successfully treat neovascularisation of the

retina, without damaging eyesight, which was a major breakthrough(3).

The next big step for skin laser treatment was with the advent of Q-

switched lasers(4), in particular the q switched Nd-YAG laser.This was

able to produce ultra short pulses of light in the giga watt range of

peak energy. Tattoo destruction became possible because ink pigment

absorbed well at this wavelength, so producing superheated water and

plasma wave formation, which could disrupt the tattoo and lead to its

dissolution. Q switching was invented in 1961, but it was not used

clinically until 1967, although the Nd-YAG laser had been produced in

1964.

During the 1970’s all of these systems were extensively used on

dermatological patients, with varying degrees of success, the use of

the Nd-YAG laser in angioma treatment being published, again by

Goldman, in 1973. The next major breakthrough came in the early

1980’s, when Anderson and Parrish published their theory of Selective

Photothermolysis(5). At the same time the pulsed dye laser was

produced, and this led to much more successful treatment of skin

vascular lesions, and spawned the development of other long pulse

systems such as the KTP (potassium titanyl phosphate - a frequency

doubling crystal used with Nd-YAG), Alexandrite, and long pulse Ruby.

These systems allowed the selective treatment of hair follicles, and

led to laser hair removal, approved by the FDA in 1989(6). More than

25 years after it had become the first laser ever created, the Ruby

resurfaced as the first laser licenced for this application by the

FDA.

Flash scanner technology, mainly used with the Carbon Dioxide laser,

was also invented in the late 1980’s and this allowed safe non

scarring laser skin resurfacing and skin blemish vapourisation(7). The

advent of the Erbium-YAG laser in 1996 led to fractional

photothermolysis and fractional skin resurfacing for lines and

wrinkles.

From the mid 1970’s onwards, an additional technique, Photodynamic

Therapy, was developed, and was initially used in urology and head

and neck cancer, newer more powerful photosensitising drugs making

treatment more effective(8). Development of this technique for skin

has created a large workload in skin premalignancy and malignancy.

2) Physics

Maiman produced the first ever laser in 1960, following its

postulation in 1916’s theory of stimulated emission by Einstein(9).

Maiman’s was a Ruby laser, producing photons of 694 nanometres (nm)

wavelength. There are many different types of laser, all producing

different wavelength (colour) of light. Table 1 is not an exhaustive

list, but demonstrates the range of wavelengths available, from 193nm

to 10,600 nm. The name of the laser tends to be called after the

lasing medium, ie the substance that is creating the laser light, such

as Carbon Dioxide (CO2). Not all compounds can be lasing media, there

is a unique property of lasing compounds that others do not have. This

is the ability to maintain a metastable state when excited.

The acronym LASER stands for light amplification by the stimulated

emission of radiation. This means that a situation is created where

stimulated emission can occur - which is when more than half of the

photons in a population are in their excited state, and by being

metastable they are able to stay there. Stimulated emission itself is

a physical situation whereby photons spontaneously emitted as an

excited atom returns to its ground state (after Plank’s law that

energy is constant - ie if an excited, energised atom returns to a

lower energy state, then the energy difference must be emitted as

something exactly equal, such as a photon in this case), then the

emitted photon can interact with other excited atoms and produce its

own identical clone - one photon stimulates the emission of another.

If this process occurs inside an optical cavity, where there is a

cylinder containing the lasing medium, and two mirrors at either end,

both exactly lined up with each other, then those photons produced

directly in line with the mirrors will bounce back and forwards

between the mirrors, stimulating their clones to be produced by

stimulated emission, all happening at the speed of light, such that

very quickly there are billions of identical photons oscillating

between the 2 mirrors. If one mirror is then made fractionally less

than 100% reflecting, ie allowing some photons to escape through a

small 99.7% reflecting area, you suddenly have an external beam of

light - a laser beam.

This light beam will have these 3 very useful properties, ones that

separate it from non-laser light sources, even high intensity ones:

1) The light will be monochromatic - which means the same colour, or

the same wavelength. This is very important when using the principle

of selective photothermolysis (see later) to treat hair or vascular

anomalies.

2) The light will be coherent - which means all the photons will be in

phase, and more importantly for medical applications, the photons will

be collimated - in parallel with each other. This means that if the

laser light is shone onto a high quality lens, the entire light beam

can be focussed onto a tiny spot, measured in microns, giving

extremely high energy densities. This is very useful in techniques

using the principle of thermal relaxation (see later), such as laser

skin resurfacing.

3) The light is high intensity, due to the amplification process (see

above). Extremely high intensity pulses can be produced by using Q

(quality) switching, a process in which a very short duration switch

is placed in the laser cavity, causing huge energy pulses of extremely

short length. This technique is used mainly in tattoo removal (see

later).

Table 1

Wavelength (nm) Laser Main Chromophore

193 Argon-fluoride excimer DNA, protein

488, 514.5 Argon Haemoglobin

532 Potassium Titanyl Phosphate (KTP)

Haemoglobin

577-595 Pulsed Dye Haemoglobin

694 Ruby Melanin, Tattoo ink

755 Alexandrite Melanin, Tattoo ink

1064 Neodymium-YAG (Nd-YAG) Tattoo ink, Melanin (less)

2940 Erbium-YAG Water

3200 Holmium-YAG Water

10600 Carbon Dioxide Water

Understanding the interaction of laser light and skin will supply the

reader with an excellent background to understand the application of

laser technology all over the body. Because facial skin is directly

visible - its what we mainly see when we look at people, the need to

avoid scarring during treatment was paramount in the development of

the laser in Facial Plastics. After Goldman’s initial experimentation

in the 60’s and 70’s, this development work was carried out

substantially at Harvard Medical School by John Parrish, a physician

at Massachusetts General Hospital, and Rox Anderson, a laboratory

technician and then medical student(10). Initially they looked at the

properties of skin from an optical point of view, then in the mid

eighties they developed 2 important physics principles of particular

relevance to the skin, namely:

1) Selective photothermolysis

2) Thermal relaxation time

1) The principle of Selective Photothermolysis was published in

Science(5). In this article, it was shown that short duration of

light, at a specific wavelength matched to the chromophore (light

absorbing tissue) make up of the target disease, could cause severe

damage to the target if energy levels were sufficiently high, but less

damage to the surrounding normal tissue. This paved the way for

selective treatment of haemangiomas, tattoos and hair removal, amongst

others, by destroying the disease but leaving the overlying skin and

subcutaneous tissue undamaged..

2) Thermal relaxation time of tissue, which is a function of its

cooling down time, was part of the initial theory of Selective

Photothermolysis, further expanded and defined. It describes the

principle that if energy is delivered in pulses of a duration less

than the thermal relaxation time of the target, then lateral heat

spread into normal tissue, which causes normal tissue damage -

scarring etc, will be minimal(11). Since physicists were working on

ways of increasing the energy of pulses whilst keeping pulse duration

the same, this allowed the removal of target tissue by instant

vapourisation as the laser beam was incident on the tissue, with

little or no collateral damage. Techniques such as Superpulse and

Ultrapulse use this, as do flashscanners.

Table 2

Target Size in microns Thermal Relaxation Time

Tattoo ink particle 1 10 ns

Melanocyte 1 1 us

Red blood cell 7 20 us

Epidermis 50 1 ms

Blood vessel (varies) 50 1 ms

Ectatic blood vessel 100 15 ms

Hair Follicle 200 100 ms

Characteristics of light as it interacts with tissue.

When light is shone on living tissue such as the skin, it does all of

the following.

1) It reflects off the surface and hits something else

2) It is absorbed by the tissue, causing an effect - this is mostly

what we are after (Grotthus-Draper law).

3) It transmits through the tissue, possibly being absorbed deeper in.

4) It scatters, so reducing the energy density and giving a wider,

less predictable effect.

3) Lasers Used in Facial Plastics

The Carbon Dioxide (CO2) Laser. This is an infrared laser, producing

light at 10,600nm wavelength. It is well outside the visible range,

and therefore needs to be combined with a visible low power aiming

beam laser, the Helium-Neon laser, which produces light at 630 nm

wavelength, in the middle of the red spectrum. The Carbon Dioxide

laser light is very highly absorbed by water, which means it has

minimal penetration in most tissue, hence it is good for superficial,

delicate effects, in particular skin and vocal cords. It will not pass

down solid quartz laser fibres however, and this can limit its

delivery deep into tissue. Flash scanning technology has greatly

helped the application of this laser in Facial Plastics(12). Flash

Scanners enable a highly focussed small laser spot (0.2mm diameter) to

be rapidly moved around a much larger area, so that the whole area is

covered in a given time, but the dwell time of the smaller spot of

0.2mm diameter is 1 millisecond or less. The dwell time if the amount

of time the laser light was actually incident on the tissue, and is

very important in minimising deeper damage, as per the theory of

thermal relaxation. For skin, the thermal relaxation time is thought

to be around 1 millisecond, so this scanner allows treatment diameters

from 3 to 10 mm to be treated quickly and evenly, all within the

thermal relaxation time, hence with minimal deep damage. The

flashscanner system relies on 2 mirrors rotating opposite each other,

but not directly opposite, so an even beam is created with even light

distribution around the entire area of the visible spot.

Superpulsing is an electronic way of stacking pulses to create pulses

of light of very high intensity and short duration - another way of

ensuring the dwell time is less than 1 msec, avoiding collateral

damage but causing a vapourising effect.

The Erbium YAG laser. This is a solid state, crystal laser, where the

lasing medium is Erbium incorporated into a garnet made from Ytrrium

and Aluminium (a garnet is a form of crystal). This is doped with

Erbium to produce light at 2,300nm wavelength. This has an even higher

water absorption peak than CO2, and is therefore even more delicate.

Er-YAG laser light passes well down solid fibres, so can be used

deeper in the body.

Vascular lasers. There are more than one lasers which fill this role.

They are all based on a wavelength between 480 and 530 nm, the yellow-

green part of the visible spectrum, which coincides with the peak of

absorption of oxygenated and deoxygenated haemoglobin - the key

chromophore in blood vessels. They include the flashlamp pumped dye

laser, the KTP (potassium titanyl phosphate), the argon laser and the

copper vapour laser. Nowadays the mainstay vascular lasers are the

first two.

Q-switched lasers. These lasers are mainly used for tattoo removal, so

do not have a big role in facial plastics. Q (quality) switching uses

an electronic switch within the laser cavity, which turns on and off

at very high frequency, causing very high energy pulses of extremely

short duration to be created. When these very high energies hit an

absorbing medium (chromophore) of the correct wavelength, explosions

of plasma are produced within the target tissue, which shatter the ink

particles within the tattoo, and are then taken away by the lymphatic

system. These laser will not be further discussed in this chapter.

Long pulsed penetrating lasers for hair removal. As their name

suggests, these lasers have a wavelength in the near infrared region,

which maximises penetration through tissue. They are used to treat

melanin accumulation in the hair follicles, causing extreme heating

and destruction of the follicle, without significantly damaging skin.

Melanin has its peak of absorption at a lower wavelength, but if these

wavelengths were used, there would be insufficient penetration to

damage the follicles, which lie quite deep in the dermis. The longer

wavelength is therefore a compromise between penetration and effect.

The main lasers in this area are the Ruby, Alexandrite, Neodymium-YAG

and Diode systems.

Photodynamic Therapy (PDT)

This is a cancer based treatment using a drug light combination to

destroy cancers at a cellular level, hence enabling retention of

tissue architecture, allowing non ablative cancer tissue removal, with

an additional selective effect due to cancer cells being more avid for

photosensitising compounds than normal tissue. Lasers for PDT are

designed for the peaks of the photosensiting compounds, mainly in the

red spectrum. Mostly nowadays they are Diode based (13), although

originally tuneable dye laser were used.

Intense Pulsed Light

A non-laser light system, it has a role to play in Facial Plastic

surgery, and so should be included in this chapter.

IPL systems use broadband flashlamps, rather like an arc light one

might use at home for exterior lighting. Emitted light tends to be in

the 500-1300 nm range, and can be modulated by cutoff filters to

narrow the emitted band. this is particularly useful if heating is to

be avoided, as infrared wavelengths above 1000 nm will be absorbed by

water, as this can cause thermal damage. Also, when treating pigmented

skin, filters can cut off the shorter wavelengths where Melanin

absorption is highest. Multiple problems can be addressed in one

treatment, such as hair removal, photorejuvenation and vascular

disorders(14).

4) Clinical areas in Facial Plastics where the laser is effective.

Benign facial lesion removal.

Many cases in facial plastics are for the removal of unsightly

blemishes, raised lumps, nodules etc. If they are removed surgically,

even with the best hands there will be a scar, and usually small

stitch marks. In the middle third of the face, this can leave long

standing mild disfigurement. Use of the CO2 laser in flash scanned

mode or Erbium-YAG delivered within a scanning module means that

facial lesions can be accurately vapourised down to the dermis, from

where skin will regenerate and form a new epidermis, with barely any

noticeable residual cosmetic defect. This is performed under local

anaesthetic with local infiltration of xylocaine 2% and adrenaline

1:200,000. Care needs to be taken that the lesion treated does not

represent anything more serious - for this a good history and

examination under the microscope or dermatoscope is required. In

particular it is important that the area treated has been present for

several years, is very slow growing / not growing at all, it has not

changed shape or colour/ darkened, or bled on minor contact. It should

also have an intact covering with no raised edge or ulceration. If

these parameters are correct, it is reasonable to go ahead and perform

laser vapourisation, there is no specimen with this procedure. If you

are worried about skin cancer or dysplasia, a biopsy may be required

before vapourisation. If malignant melanoma is suspected, wide

excision by a dermatological oncologist should be performed.

Rhinophyma

This condition, usually associated with Acne Rosacea, is characterised

by hypertrophic skin thickening on the external nose, most prominent

at the nasal tip. The thickening is mainly epidermal, and this lends

itself to vapourisation much more deeply than one could risk when

treating facial moles, as the underlying dermis may be 20 mm or more

away. The aim of treatment is to avoid deep dermal damage which would

cause scarring, but remove all of the excessive and disfiguring skin

tissue. This can be easily achieved using the scanned Carbon Dioxide

laser in high power mode, stopping when the deeper tissues are

uncovered. This sculpting mode of use has replaced the old fashioned

way of treating this disease by slicing off the redundant tissue with

a scalpel, a technique that was bloody and uneven at best.

Laser skin resurfacing

The ability to accurately remove superficial layers of skin without

significant deep dermal damage by using flash scanners has become one

of the main applications of the CO2 and Erbium-YAG laser in facial

plastics. Using the correct parameters, keeping energy delivery to

within the thermal relaxation time of the tissue (for skin,

approximately 1 millisecond) skin can be bloodlessly removed in 30

micron (um) deep layers (15). With each pass of laser light, heat is

delivered deeper into tissue, such that the epidermis vapourises away

and is removed by using cotton wool soaked in saline, leaving the

papillary dermis. Since this has different light absorption

characteristics, and much higher collagen content, instead of being

vapourised, it is mainly heated, causing visible dermal collagen

contraction, and significant skin tightening (16). The dermis and

epidermis then reforms due to migration of dermal cells from skin

appendages, leaving the area treated with a new, fresher outer layer

of skin, and dermal collagen tightening (17). It is a very effective

rejuvenating treatment. Postoperative healing can take weeks however,

and its is not a procedure for the faint hearted, particularly if the

whole face is treated. Quite elaborate pre and post treatment

protocols are followed to minimise the risk of damage and scarring.

Most resurfacing is done for the ageing face (lines and wrinkles),

although results from acne treatment with mild to moderate pitting are

also excellent.

Newer techniques use lasers to drill holes in the skin, rather than

completely removing the superficial layers. This is called fractional

photoablation and has less post operative effect in terms of redness

and swelling. It is less effective however, and studies have looked

into using a combination of traditional laser resurfacing for the

epidermis (1 pass) followed by fractional treatment of the reticular

and papillary dermis. This is called ablative fractional

photothermolysis(18). The Erbium-YAG laser can also be used for skin

resurfacing, although it has generally been found to be too slow and

ineffective as its penetration through skin is significantly less than

the CO2 laser, so less effect/damage is achieved. Multiple pass

techniques with this laser have been found to be nearly as effective

as the CO2 laser however and with better healing (19). Non-ablative

tissue remodelling uses deeper penetrating lasers to damage collagen

and cause it to shrink, without causing a significant epidermal

injury. Tissue cooling is important in this area (20). Lasers such as

the 1320 nm Nd-Yag, 1540 Erbium-glass and 1450 nm diode have been used

for this (21).

Transconjunctival blepharoplasty

In this procedure, the CO2 laser can be used to incise the inferior

(caudal) conjunctiva allowing access to the fat pad beneath. The

advantages of using the laser as a knife is that it cuts the slightly

loose conjunctiva easily, avoiding bleeding and haematoma / black

eyes, and also preventing shearing and tearing of the conjunctiva

which happen when the scalpel or scissor is used. Care has to be

taken with the proximity of the cornea, and corneal protectors are

recommended.

Vascular lesions

Because the absorption spectrum of oxygenated and deoxygenated

haemoglobin is relatively wide, a number of lasers fit into this

category. What is key about the treatment of vascular lesions on the

face is that the size and depth of the lesion be accurately assessed,

and that the laser used can provide a variable spot size and pulse

duration to allow effective treatment. The use of ultrasound can help

in this area. Vascular lesions on the face range from thread veins

over the cheek and nose, often caused by sun damage, to port wine

stains. The smaller lesions, such as thread veins, spider naevi,

arterio-venous malformations are easy to treat, and the 532 nm KTP

Aura laser gives an adequate range of pulse duration, energy and spot

size for most of these. Larger lesions such as haemangiomas contain

significantly bigger blood vessels, so longer pulses and therefore

more power is needed. The flashlamp pumped dye laser gives better

penetration and coverage for these (22).

Hair removal

Permanent hair removal is possible if selective photothermolysis (5)

is used to irreversibly damage a chromophore in the hair follicle,

whilst minimally damaging the same chromophore in the skin around the

follicle. The main chromophore found in hair follicles is melanin,

therefore all lasers used in this area emit light at the near infrared

end of the spectrum, where there is reasonable melanin absorption and

good penetration.This is now the biggest area for the use of lasers on

the skin. Facial hair, particularly in females, can be a big problem.

Female hirsutism affects 2-10% of the female population.

Up until the introduction of laser hair removal by Noren in 1996

(pers comm.), facial hair treatment, apart from shaving, essentially

involved pulling the hairs out, only for further growth to occur soon

after. Depilatory creams and electrolysis were also used, to limited

effect. Hypertrichosis, in which hair growth suddenly increases,

usually in patches, may be caused by drugs such as Phenytoin or

Cyclosporine, although it can also be a sign of internal malignancy.

Full investigation is required before treating these patients. General

facial hair problems in females is often linked to polycystic ovaries,

but does not require further investigation.

There is a choice of lasers which can be used for this procedure.

Which one the doctor chooses often depends on his or her population to

be treated. The ideal patients has white skin containing no melanin,

and black hair, with lots of melanin in the hair and its follicle. In

these cases high energies can be used, as there will be no chance of

dermal-epidermal melanin being damaged. The Fitzpatrick skin type

classification is useful in choosing which laser system to use. It is

based on a scoring system looking at eye and hair colour, skin colour

and its reaction to sunlight.

The Fitzpatrick Scale:

● Type I Light, pale white. Always burns, never tans

● Type II White; fair. Usually burns, tans with difficulty

● Type III Medium, white to olive. Sometimes mild burn, gradually

tans to olive.

● Type IV Olive, moderate brown. Rarely burns, tans with ease to a

moderate brown.

● Type V Brown, dark brown. Very rarely burns, tans very easily

● Type VI Black, very dark brown to black. Never burns, tans very

easily, deeply pigmented

Many techniques have been used to try and avoid skin heating in

Fitzpatrick types 2 and above. These include cooled air blowing, cold

spray blowing, frozen glass slides, ice packs, topical steroids (23).

It remains a problem as superficial skin damage may cause disordered

pigmentation, which is cosmetically difficult to cover/treat.

Table 3

Laser Skin type Wavelength nm

Long pulse Ruby 1-3 694

Long pulse Alexandrite 1-4 755

Pulsed diode 1-4 800-810

Long pulse Nd-YAG 1-6 1064

IPL 1-4 590-1200

As the table shows, increase in wavelength means darker skin can be

treated, as Melanin absorbs at lower wavelengths. When choosing energy

density measured in Joules/cm2, thjis depends on the immediate

treatment response, in which perifollicular oedema and mild erythema

should be seen, both of which resolve after 60 minutes. Test

treatments are often used to identify the correct treatment

parameters.

Skin Cancer

Non-Melanoma skin cancers can be effectively treated using the carbon

dioxide laser, or photodynamic therapy.

The Carbon Dioxide laser can be used as a bloodless knife to closely

follow surgical markings around skin cancers, allowing accurate

raising of flaps and z plasties. The spot size of 200 microns, when

used in Superpulse mode allows a neat scar with almost no collateral

damage. The lack of bleeding means that it is easier for the operator

to follow premarked lines for incision, which can often be complicated

in facial plastic surgery, and minor bleeding into the wound after

suturing, which is often the cause of poor scars, is also avoided.

The Carbon Dioxide laser in Flash Scanned mode, using spot sizes of

around 3 mm diameter, can also be used to superficially vapourise

areas of dysplasia, which heal without scarring. Also small basal and

squamous cell carcinomas can be vapourised away down to normal tissue

as in the Moh’s technique. Reconstruction is often not necessary as

the resultant defect, a depression in the skin, is less cosmetically

disfiguring than reconstruction with local flaps.

Photodynamic Therapy is a relatively new technique used for BCC’s or

SCC’s (24). It relies on a drug-light interaction causing activation

of a previously inert substance (the photosensitiser) so that it

reaches a triplet state, subsequently decaying in 2 stages back down

to the ground state, with resultant release of energy at the correct

level to break the covalent bond of the oxygen molecule. This causes

singlet oxygen to be produced, which immediately oxidises vital

intracytoplasmic organelles, causing cell death in a manner which

mimics apoptosis. This all means the tissue architecture is preserved,

since this is a non-ablative treatment and allows migration of

adjacent cells into the area where PDT was performed, with resultant

healing superior to secondary intention, and with no scar as would be

seen with excision and primary intention healing. Selectivity can

occur with respect to the cancer and normal tissue. This is highly

desirable as it minimises normal tissue damage. The best way to gain

selectivity is to paint the photosensitising agent directly onto the

tumour. This is the basis of treatment with d-Amino Laevulinic acid,

which absorbs well into tumours, and causes build up of Protoporphyrin

IX, which is an endogenous photosensisitiser(25). Unfortunately no

other photosensitisers will absorb directly into tissue.

Their delivery is therefore systemic, either orally (ALA again) or

intravenously - most of the mainstream photosensitising agents.

Systemic delivery will lead to some selectivity, as there is increased

affinity for photosensitisers by cancer cells when compared to normal

tissue. Once the peak levels of drug are in the cancer (this can be

measured using fluorescence), activating light of the correct

wavelength, intensity and fluence is shone at the skin cancer. The

method of cell death and healing leaves little residual

scar/deformity.

Photodynamic therapy is limited in its efficacy as specific energy

transfer in the formation of singlet oxygen means that the maximum

wavelength of light that can be used is at around 740 nm. This limits

tissue penetration and therefore depth of effect, to about 7 mm when

using the most powerful second generation photosensitisers.

5) Pigmentation Problems

One of the inherent features of skin is its ability to react to light

by producing melanin, from Melanocytes, which are cells of the Dermis-

Epidermis border. This is a protective function, mainly aimed at

preventing ultraviolet radiation damaging the skin.

Lasers, being light, have the ability to stimulate superficial

melanocytes. They may either cause overproduction or underproduction

of melanin, leading to Hyperpigmentation (over) in the treated area,

or hypopigmentation (under). The lasers that are most dangerous are

those whose wavelength is around 500 nm - 600 nm, where the pigment

Melanin absorbs light the most strongly. Other damaging lasers are the

ablative ones, such as the Carbon Dioxide laser in skin resurfacing.

Although this do not cause a direct light-chromophore effect on

Melanin, the Carbon Dioxide laser causes an intense inflammatory

effect, and that can also cause hyper or hypo pigmentation. Those of

Fitzpatrick skin types 3 and 4 have the most active melanocytes, and

are most prone to damage. People with a recent sun tan will also have

active melanocytes and should not be treated with any skin laser until

the tan has faded significantly. The Cycline family of antibiotics,

particularly tetracycline, are associated with skin pigment changing

after laser treatment. A 6 month gap between the last antibiotic

treatment and the commencement of laser treatment is usually required.

6) Safety

Standard laser safety procedures should be in practice at all times

when class 4 (all medical) lasers are in use. Eye protection for those

in the treatment rooms, locked doors and proper signage are all

required. The wavelength range 400-1400 nm can cause retinal damage,

and the adage never look at a laser beam must be adhered to.

When operating very close to the eyes use stainless steel corneal

protectors, as sudden head movements in response to pain can cause the

laser beam to hit directly onto the cornea, causing corneal scarring

and partial blindness, particularly with the Carbon Dioxide laser.

Other issues such as use of inflammable materials near the laser beam

need to be considered, particularly when 100% oxygen is around, as

this can pool since it is heavier than air. The laser beam is a very

good igniter, particularly the Carbon Dioxide laser.

Skin healing after laser treatment is obviously very important. Often

the skin appendages are very involved in this. The recent use of

retinoids such as Accutane or Roaccutane precludes most laser

treatments as this drug reduces the number of sebaceous glands which

can be vital for skin healing. Generally a 6 month gap is required

before treatment.

7) References

1) Maiman T.H. (2000). The laser odyssey. Blane, Laser Press.

2) Goldman L, Blaney D.J., Kindel D.J Frankie E.K. (1963) Effect of

the laser beam on the skin. J. Invest. Dermatol. 40:121-122

3) Campbell C.J., Noyori K.S., Rittler M.C., Koester C. (1965) Retinal

coagulation: Clinical studies. Ann. N.Y. Acad Sci. 122:780

4) Hellwarth R.W., McClung F.J. (1962) Giant pulsations from Ruby.

Appl. Phys. 33:838-841

5) R. Rox Anderson and John A. Parrish (1983) Selective

Photothermolysis: precise microsurgery by selective absorption of

pulsed radiation

Science Vol. 220, No. 4596, pp. 524-527

6) Sherwood K.A., Murray S., Kurban A.K., Tan O.T. (1989) Effect of

wavelength on cutaneous pigment using pulsed irradiation. J. Invest.

Dermatol. 92:717-720

7) Pulsed CO2 laser tissue ablation: Effect of tissue type and pulse

duration on thermal damage Joseph T. Walsh,Thomas J. Flotte, R. Rox

Anderson,Thomas F. Deutsch. Lasers in Surgery and Medicine. Volume 8,

Issue 2, pages 108–118, 1988

8) Dilkes MG, DeJode ML, Gardiner Q, Kenyon GS, McKelvie P. Treatment

of head and neck cancer with photodynamic therapy: results after one

year.

J Laryngol Otol. 1995 109(11):1072-6.

9) Einstein A., Zur quantumtheorie der Strahlung. (1917) Physikalishe Gesellschaft Zurich. 18:47-62

10) R Rox Anderson and John A Parrish. The Optics of Human Skin.

Journal of Investigative Dermatology (1981) 77, 13–19

11) Anderson RR, Parrish JA. Microvasculature can be selectively

damaged using dye lasers: a basic theory and experimental evidence in

human skin. Lasers Surg Med.1986;122:1016-1022

12) Lach E. Flash scanning the CO2 laser: a revival of the CO2 laser

in plastic surgery (1994) , Proc. SPIE 2128, Laser Surgery: Advanced

Characterization, Therapeutics, and Systems IV, 211

13) An in vivo comparison of the photodynamic action of a new diode

laser and a copper vapour dye laser at 652 nm (1996)

DeJode, M. L.; Mcgilligan, J. A.; Dilkes, M. G.

Lasers in medical science 11 (1996), S. 117-121

14) Schoenewolf N., Barysch M and Dummer R. 2011. Intense Pulsed

Light. In: Curr Probl dermatol. 42:166-172

15) Alster T, Kauvar A, and Geronimus R. (1996) Histology of high

energy pulsed CO2 laser resurfacing. Semin Cutan Med Surg; 15:189-93

16) Green J, Burd E., Nishioka N (1992) Middermal wound healing. A

comparison between dermatomal excision and pulsed carbon dioxide laser

ablation. Arch Dermatol.;128:639-45

17) Ross E, Naseef G, Skrobal M. (1996). In vivo dermal collagen

shrinkage and remodeling following CO2 laser skin resurfacing. Lasers

Surg Med;8:38

18) Cohen S, Henssler C, Johnston J (2009) Fractional photothermolysis

for skin rejuvenation. ... In vivo histopathologic comparison of the

acute injury following treatment with five fractional ablative laser

devices.Dermatol Surg 37(6):776–781

19) Tanzi EL, Alster TS (2003) Single pass carbon dioxide versus

multiple-pass Er:YAG laser skin resurfacing. Comparison of

postoperative wound healing and side effect rates. Dermatol Surg 29 :

80-84 35.

20) Anderson R.R. (2000) Lasers in dermatology: A critical update. J

dermatol;27:700-5

21) Hardaway C and Ross E. (2002) Nonablative laser skin remodelling.

Dermatol Clin.;20:97-111

22) Garden J, Polla L, Tan O. (2006) Laser treatment of vascular

lesions. Clin Dermatol.;24:8-15. 9.

23) Drosner M and Adatto M. (2005) Photoepilation: Guidelines for care

from the European Society for Laser Dermatology. I. Cosmetic Laser

Ther;7:33-38

24) Wilson B and Mang T. (1995) Photodynamic therapy for cutaneous

malignancies. Clin. dermatol.;13:91-6

25) Kennedy J. Pottier R., Pross D. (1990) Photodynamic therapy with

endogenous protoporphyrin IX: Basic principles and present clinical

experience. J. Photochem. Photobiol B;14:275-92