Lasers in dermatology
The first lasers used to treat skin conditions occurred over 40 years ago. Argon
and carbon dioxide (CO2) lasers were commonly used to treat benign vascular birthmarks such as port-wine stains
and haemangiomas. Although these birthmarks could be effectively lightened, a side effect was the unacceptably high rate of
scar formation. In the last 20 years major advances in laser technology has revolutionised their use in the treatment of many
skin conditions and congenital defects, including vascular and pigmented lesions, and the removal of tattoos, scars and wrinkles.
Properties of laser light
‘Laser’ is an acronym: light amplification
by the stimulated emission of radiation.
Lasers are sources
of high intensity light with the following properties:
- Monochromatic i.e. the light is of a single wavelength
- Coherent i.e. the light beam waves are in phase
- Collimated i.e. the light beams travel in
parallel
Laser light can be accurately focused into small spots with very high energy.
The
light is produced within an optical cavity containing a medium, which may be a gas (e.g. argon, krypton, carbon dioxide),
liquid (e.g. dye) or solid (e.g. ruby, neodymium:yttrium-aluminium-garnet, alexandrite). The process involves excitation of
the molecules of the laser medium, which results in the release of a photon of light as it returns to a stable state. Each
medium produces a specific wavelength of light, which may be within the visible spectrum (violet 400 through to red 700nm)
or infrared spectrum (more than 700 nm).
Vascular skin lesions contain oxygenated haemoglobin, which strongly absorbs
visible light at 418, 542 and 577 nm, whereas pigmented skin lesions contain melanin, which has a broad range of absorption
in the visible and infrared wavebands. Infrared lasers are broadly destructive because they are absorbed by water in and between
skin cells (these are composed of 70-90% water).
The aim is to destroy the target cells and not to harm the surrounding
tissue. Short pulses reduce the amount that the damaged cells heat up, thereby reducing thermal injury that could result in
scarring. Automated scanners aim to reduce the chance of overlapping treatment areas.
What types of lasers are there?
There are several types of lasers used in skin laser surgery. Older laser technologies such as the continuous wave (CW)
lasers of CO2 and argon have been largely replaced with quasi-CW mode lasers and pulsed laser systems. The wavelength
peaks of the laser light, pulse durations and how the target skin tissue absorbs this, determine the clinical applications
of the laser types.
| Laser type | Laser
source | Wavelength peaks |
| CW: emit a constant beam of light with
long exposure durations | CO2 | 10,600 nm |
| |
Argon | 488/514 nm |
| Quasi-CW: shutter the CW beam into
short segments, producing interrupted emissions of constant laser energy | Potassium-titanyl-phosphate
(KTP) | 532 nm |
| | Copper vapour/bromide |
510/578 nm |
| | Argon-pumped tunable dye (APTD) |
577/585 nm |
| | Krypton | 568 nm |
| Pulsed*: emit high-energy laser light in ultrashort pulse durations with relatively long intervening time periods
between each pulse | Pulsed dye laser (PDL) | 585-595 nm |
| |
QS ruby | 694 nm |
| | QS alexandrite |
755 nm |
| | QS neodymium (Nd):yttrium-aluminum-garnet (YAG)
| 1064 nm |
| | Erbium:YAG | 2490
nm |
| | CO2 (pulsed) | 10,600 nm |
| * Pulsed laser systems may be either long-pulsed such as PDL with pulse durations ranging
from 450ms to 40millisec, or very short-pulsed (5-100ns) such as the quality-switched (QS) lasers. |
What skin conditions can be treated with lasers?
Vascular lesions
Lasers have been used successfully
to treat a variety of vascular lesions including superficial vascular malformations (port-wine stains), facial telangiectases, haemangiomas, pyogenic granulomas, Kaposi sarcoma and poikiloderma of Civatte. Lasers that have been used to treat these conditions include argon, APTD, KTP, krypton, copper vapour, copper bromide, pulsed dye lasers and Nd:YAG. Argon (CW) causes a high degree of non-specific thermal injury and scarring and is now largely
replaced by yellow-light quasi-CW and pulsed laser therapies.
The pulsed dye laser is considered the laser of choice
for most vascular lesions because of its superior clinical efficacy and low risk profile. It has a large spot size (5 to 10mm)
allowing large lesions to be treated quickly. Side effects include postoperative bruising (purpura) that may last 1-2 weeks and transient pigmentary changes. Crusting, textural changes and scarring are rarely seen.
The new V-beam features provide ultra-long pulse duration so greater is energy directed at the target blood vessels over
a longer period of time, resulting in more uniform blood vessel damage. This reduces the purpura seen with the earlier pulse
dye lasers. The addition of dynamic cooling increases comfort during treatment enabling higher fluencies (energy) to be delivered
safely and effectively, so fewer treatments are required.
Vascular malformations associated with smaller more superficial
blood vessels respond better to treatment than deeper larger vessels (more often arising in older individuals). It is therefore
best to begin treatment early. Fading by 80% occurs after 8 to 10 treatments on average. Further treatment may be necessary
if the lesion recurs.
Treatment with quasi-CW lasers also produce effective outcomes but they are may be associated
with higher incidences of scarring and textural changes. The most common side effects include mild erythema, oedema, and transient
crusting.
Non-laser intense pulsed light devices can also be used for treating vascular lesions.
 | 
Bruises day after treatment |
Pulse dye laser treatment
Pigmented lesions and tattoos
Melanin-specific, high energy, QS laser systems can successfully lighten
or eradicate a variety of pigmented lesions. Pigmented lesions that are treatable include freckles and birthmarks including some congenital melanocytic naevi, blue naevi, naevi of Ota/Ito and Becker naevi. The short pulse laser systems effectively treat the lesions by confining their energy to the melanosomes, which are the
tiny granules containing melanin inside the pigment cells. The results of laser treatment depend on the depth of the melanin
and the colour of the lesion and is to some degree unpredictable. Superficially located pigment is best treated with shorter
wavelength lasers whilst removal of deeper pigment requires longer wavelength lasers that penetrate to greater tissue depths.
Caution is needed when treating darker-skinned people as permanent hypopigmentation and depigmentation may occur. Successfully
treated lesions may recur.
Prior to any laser treatment of pigmented lesions, any lesion with atypical features
should be biopsied to rule out malignancy. The treatment of congenital melanocytic naevi is a controversial issue. The long-term
effect of using lasers on promoting melanoma is not known but the treatment is thought to be low risk.
The QS laser systems can selectively destroy tattoo
pigment without causing much damage to the surrounding skin. The altered pigment is then removed from the skin by scavenging
white blood cells, tissue macrophages. The choice of laser depends on the colour, depth and chemical nature of the tattoo
ink. Two to ten treatments are often necessary. Yellow, orange and green colours are the most difficult to remove.
-
Black: QS ruby, alexandrite or Nd:YAG
- Blue and green: QS ruby, alexandrite
- Yellow, orange,
red: QS Nd:YAG or PDL
As with other laser treatments, pigmentary and textural changes including scars
may occur.
Hair removal
Lasers can be used to remove excessive and cosmetically disabling hair due
to hypertrichosis or hirsutism. Laser treatments remove dark hair quickly and it may take 3 to 6 months before regrowth is evident. Several treatment cycles
are required with the spacing between treatments dependent on the body area being treated. Laser treatments are less painful
and much quicker than electrolysis. Complications are rare but superficial burns, pigmentary changes and even scarring may occur. Increased growth of fine dark
hair in untreated areas close to the treated ones has been reported.
Suitable devices include long-pulsed ruby
and alexandrite lasers, diode (810nm), millisecond Nd:YAG and non-laser intense pulsed light.
Epilation | 
Temporary dark marks | 
Permanent white marks |
Laser hair removal
Facial wrinkles, scars, and sun-damaged skin
Facial laser resurfacing uses high-energy, pulsed and scanned
lasers.
Pulsed CO2 and erbium:YAG lasers have been successful in reducing and removing facial wrinkles, acne scars and sun-damaged skin. High-energy, pulsed, and scanned CO2 laser is generally considered the gold standard against which all other
facial rejuvenation systems are compared. Typically a 50% improvement is found in patients receiving CO2 laser treatment. Side effects
of treatment include post-operative tenderness, redness, swelling and scarring. The redness and tenderness last several weeks,
while new skin grows over the area where the damaged skin has been removed by the laser treatments (ablative laser systems).
Secondary skin infection including reactivation of herpes is also a potential problem until healing occurs. Extreme caution
is needed when treating darker skinned individuals as permanent loss or variable pigmentation may occur longterm.
Erbium:YAG produces similar results and side effects to CO2. Despite their side effect profile and long recovery
time these ablative laser systems, when used properly, can produce excellent results.
Recently non-ablative lasers
have been used for dermal modeling; 'non-ablative' refers to heating up the dermal collagen while avoiding damage
to the surface skin cells (epidermis) by cooling it. Multiple treatments are required to smooth the skin.
Keloids
and hypertrophic scars
Keloids and hypertrophic scars are difficult to eradicate and traditional treatments are not always successful. Vaporising lasers (CO2 and erbium:YAG)
have been useful as an alternative to conventional surgery. More recently PDL has been used to improve hypertrophic scars
and keloids. This may require multiple treatment sessions or the simultaneous use of intralesional injections to gain good
results. The PDL has been reported to reduce the redness as well as improving texture and pliability of the scar.
Other
uses
Lasers are sometimes used to remove viral warts by vaporization (CO2 laser) or destruction of the dermal blood vessels (PDL) but the evidence would suggest that
this is no more effective than standard wart paints or even waiting for spontaneous clearance.
The CO2
laser can be used to remove a variety of skin lesions including seborrhoeic keratoses and skin cancers by vaporization or in cutting mode. However, conventional surgery or electrosurgery can also be used and is generally less expensive.
Violet-blue metal halide light (407-420
nm) has been used to treat acne, because it has a toxic effect on the acne bacteria, Proprionibacterium acnes.
The Excimer laser uses noble gas and halogen to produce ultraviolet radiation (308 nm) that will clear psoriasis plaques. However the small spot size and the tendency to cause blistering makes treatment time-consuming and difficult to
perform.
Laser safety
Safety precautions will depend on which laser system is used and in what setting.
They should include:
- Thorough training of personnel
- Eye protection for the patient and
clinic staff
- Warning notice outside the procedure room
- Use of non-reflective instruments
- Avoidance of flammable materials.
Adverse effects of laser
Laser treatments
are basically burns, so it is not surprising that sometimes the following effects may occur.
- Temporary
pain, redness, bruising, blistering and/or crusting
- Infection including reactivation of herpes simplex
- Pigment changes (brown and white marks), which may be permanent
- Scarring, which is luckily
rare
