Lasers have been put to cosmetic use for nearly half a century and in recent decades, we have seen dramatic innovations in the types of lasers used and the various treatments they can offer. This article will give a basic overview of the types of cosmetic lasers and how they interact with our bodies.
It’s important to have a basic understanding of the structure of the skin because different lasers interact with areas in various ways. Some burn away the top layer of skin cells, while others penetrate more deeply leaving the surface unaffected. Their wavelengths can be adjusted to interact with or remove only certain colored cells like those in birthmarks or tattoos. And others still, can be used to treat serious health issues deep inside the body. But before jumping into the world of cosmetic lasers, there are some important physics and physiological concepts and terms that are important to understand.
First, is the structure of the skin. Your skin has three basic layers: the epidermis which is the protective outer layer that gives the skin its color; the dermis which contains hair follicles, sweat glands, nerve endings, and connective tissues (collagen); and the hypodermis or subcutaneous tissue made of fat and more connective tissue (more collagen). So now that we have our three major layers of skin, we can take a look at how lasers function and how each type is used in different treatments.
Lasers operate by energizing a particular medium inside the machine. This medium can be a gas, liquid, or solid matter. When energized, the molecules of the medium become excited and must return to a stable state. Upon returning to this stable state, the medium releases the energy in the form of a light photon (except there are an incomprehensible amount of photons; something like 50,000,000,000,000,000 photons in a 0.000005-second long laser pulse, give or take a zero). These photons are the light in the laser.
Sometimes this light is visible to the human eye (when the wavelength is 400 nm through to 700 nm) and other times its infrared (exceeding 700 nm). The energy travels from the laser to the skin in the form of light and when the photons are absorbed by the skin, the energy is transferred in the form of heat. This heat then destroys the cells. Different wavelengths affect cells at differing depths and can be adjusted depending on the treatment.
Another element in laser classifications is pulse duration. Cosmetic lasers are typically split into three categories:
CW produce a continuous beam with long exposure time.
Quasi-CW shutters the beam but is still a nearly steady emission
Finally, there is Q-switched which pulses the laser with extended periods between pulses. These pulses limit the amount of time the skin is exposed to thermal energy, limiting the damage to the area surrounding the target cells remain unaffected.
Below are some types of lasers categorized by pulse duration with their medium and wavelength:
Continuous Wave lasers:
One of the oldest and most common forms of laser treatment is skin resurfacing. This procedure is typically used to treat wrinkles as well as scars and sun damage. Resurfacing can be done one of two ways: ablative and non-ablative. Ablative treatments involve burning off the top layer of cells to allow new healthy cells to take their place. CO2 lasers—that is, lasers that use carbon dioxide as their medium—are the most frequently used along with erbium:YAG lasers (YAG stands for yttrium-aluminum-garnet). Non-ablative, on the other hand, penetrates through the epidermis leaving it largely intact and heats the dermis, the middle layer. This stimulates collagen production causing wrinkles to tighten. Although it is less invasive, the non-ablative procedure is generally less effective than ablative.
Lasers are frequently used to treat skin lesions, both vascular (which are discoloration caused by haemoglobin) and pigmented lesions (caused by melanin). For treating vascular lesions, the pulsed dye laser is considered to be the most effective at targeting the oxygenated haemoglobin that causes discoloration, though it may require up to a dozen sessions to significantly reduce the visibility of the malformation. Pigmented lesions can be treated with most Q-switched lasers. The short pulses are effective at eliminating the melanosomes transporting melanin. Lasers with longer wavelengths are more effective at penetrating deeper into the skin whereas shorter wavelengths are better suited for superficial lesions.
Another common use for cosmetic lasers is hair removal. Long-pulsed lasers are the most effective for removing hair. After several sessions, it typically takes 3-6 months before regrowth is evident.
In general, cosmetic laser procedures are a relatively safe and noninvasive treatment option for a wide variety of conditions. Side effects are usually contained to mild bruising or burning sensations like a moderate sunburn, or in some cases, mild scarring, especially with ablative treatments. But in order to be safe, it is crucial to remember that technicians and operators must be well trained to use these machines because more serious damage may occur such as burns or eye damage if misused.
However, there is a wide range of possibilities when it comes to lasers and the treatments they offer. We invite you to learn more on our blog and check out some of the used lasers we have to offer at Sentient Lasers.