In 1917 Albert Einstein theorised on the stimulated emission of radiation, or what we commonly refer to as lasers. Today lasers are used in a multitude of products and systems - from CD players to barcode scanners. Laser is an acronym for Light Amplification for the Stimulated Emission of Radiation and is used in the cosmetic enhancement and beauty industries for an array of treatments ranging from the correction of skin irregularities, pigmentation and wrinkles to hair reduction.

Lasers work by selecting a wavelength that is readily absorbed by the target tissue. The target tissue is heated to a temperature high enough to destroy it without damaging the adjacent normal tissue. The laser emits a single frequency of light with all the light waves going in the same direction, allowing the target tissue to absorb the maximum amount of heat. The target tissue is all-important when treating skin problems with a laser. The target tissue for pigmentation is melanin; for spider veins it is blood; and for wrinkles it is water. Each of these target tissues absorbs a different wavelength of light, meaning a different laser is needed for each specific problem.

WHAT DOES IT TARGET?

Different wavelengths allow delivery of energy to different structures. These structures are target tissues known as chromophores. For cutaneous laser therapy these are: haemoglobin (blood both oxygenated and de-oxygenated), water, melanin (pigment in hair and brown spots) and protein (tattoos).

As each chromophore absorbs different wavelengths of light, different lasers are used for different treatments. The treatments usually fall into four categories:

1. Skin resurfacing, minimising wrinkles and improving scars (chromophore is water)

2. Vascular lesions such as spider veins (chromophore is haemoglobin)

3. Pigmented lesions such as brown spots and unwanted hair (chromophore is melanin)

4. Tattoos (chromophore is protein).

HOW DOES LASER LIGHT VARY FROM OTHER LIGHT?

Laser light is different to normal light for many reasons. It travels in a synchronised fashion, retains its intensity over a long distance, is monochromatic (of the same wavelength or colour) and it can be pulsed.
The principle behind lasers is light absorption. The same as a black car will be hotter than a white car because it absorbs more wavelengths of light, certain target tissues will absorb certain wavelengths of light more effectively. As the laser light is monochromatic, the target tissue will take on maximum absorption while the surrounding tissues won't. This allows the target to be isolated and treated.

It's the colour in the structure that absorbs the colour of the wavelength. There are absorption spectra (level of absorption of particular wavelengths) outside of our normal colour vision range. We can't see ultraviolet light but it's there and is absorbed by particular structures.
Carbon dioxide (CO2) and erbium lasers emit frequencies out of our visible range and water is a very strong target tissue for them.

SO WHY DOES ABSORBING LIGHT TREAT A PROBLEM?

The light energy is transformed into heat energy. This energy heats the chromophore and causes damage. In the case of hair removal, it heats up the hair follicle to a critical temperature that causes irreversible damage to the hair follicle and only the hair follicle. Surrounding structures will be heated but not to a level where they are irreversibly damaged, otherwise blistering will appear.

For blood vessels, the haemoglobin is targeted by green or yellow light as these wavelengths are predominantly absorbed by blood. The heat causes clotting, coagulation and the closing down of small vessels. For resurfacing the skin, the target tissue is water. The laser delivers enough energy to heat the water in skin, vaporising it and in turn vaporising skin tissue. Similarly, with each treatment the heat causes damage of the target tissue, creating the desired result.

However, without energy (measured in watts) to deliver the wavelength nothing will happen. More energy increases the heat and damage, so there is a trade-off.

One of the special qualities of laser light is its ability to be pulsed. Often the beam can target the chromophore for long enough to heat it, stopping before surrounding tissues absorb too much of the light, then this process is repeated. The duration of pulse is proportionate to the size of the target.

HOW DO WE KNOW WHICH LASER?

A laser is usually named for the internal substance that gives it its specific wavelength and treatment properties. These substances can be gas (carbon dioxide - CO2 laser) liquid (dye) or solid (ruby). The operator needs to exactly assess the appropriate wavelength so as to have the energy predominantly delivered to the chromophore and not to any other structure.
For example, if the desired result is hair removal and the patient has dark skin and fair white hair, by using a laser that is predominantly absorbed by pigment, the hair follicle won't absorb much of that heat energy but the
skin will.

Similarly, when treating tattoos that are multicoloured, different wavelengths are needed for maximum absorption by each of the different pigments.

FRACTIONATED LASER TECHNOLOGY

Fractionated laser technologies, which break up the light beams to allow columns of untreated tissue to activate healing mechanisms beneath the skin's surface, have facilitated fast, relatively simple treatments for skin conditions ranging from scars and birthmarks to wrinkles.

These lasers work by creating microscopic thermal injuries that trigger collagen production, stimulating cell renewal and plumping out the tissues while the surface of the skin remains intact.

The applications for fractional laser technology include overall facial rejuvenation, improving evenness of skin tone and texture, reducing pore size, improving the appearance of lines and wrinkles and helping to reverse the effects of sun damage.

Because laser treatments use heat, a mild to moderate burning sensation is experienced during treatment and slight swelling and redness afterwards. This can be covered with makeup and normally subsides in a few days, depending on the level of treatment administered.

Ablative and fractionated laser treatments can be administered only by qualified cosmetic doctors.

SKIN RESURFACING

Ablative laser treatments are an extreme but effective method of treating acne and usually used only for severe cases because of the extended healing time involved. In the past few years, a host of new-generation lasers have been developed that require only days, as opposed to weeks, of recovery time.

Always ask how new the laser is, when it was purchased and when it was last checked by the manufacturer. Recent models are far superior to earlier ones in terms of achieving predictable and precise results with less down time.
Laser continues to gain popularity here in Australia and overseas, being offered in various forms from salons to medical facilities. In 2009 laser for hair removal was in the top five most popular non-surgical procedures, according to the American Society for Aesthetic Plastic Surgery (ASAPS). The technology it uses continues to be finessed and explored.

Australian Cosmetic Surgery Magazine #48