It does it all—from hair removal to skin rejuvenation
The word “laser” is an acronym for “light amplification by stimulated emission of radiation.” Albert Einstein first described the laser as a theoretical concept in 1917.1 Since lasers were commercially developed in the 1960s, many different laser systems have become available for use in telecommunications, industrial sciences, and numerous medical fields.
Innovations in medical lasers have made it possible for physicians to treat conditions that previously were untreatable or difficult to treat. In recent years, the main focus of research and development in medical lasers has been on hair removal, the treatment of vascular lesions (such as spider veins), and vision correction. Currently, exciting research is being conducted in the areas of nonablative laser resurfacing and improved photodynamic therapy for treating skin cancers.
The materials within the laser that are energetically stimulated determine the wavelength of the radiation produced. One particular laser that has come to the forefront of technology for multiple aesthetic medical purposes is the neodymium yttrium–aluminum garnet (Nd:YAG) laser, which uses an yttrium–aluminum garnet crystal rod with dispersed atoms of neodymium as the lasing medium. The neodymium is stimulated to emit near-infrared radiation at a wavelength of 1064 nanometers (nm).
Selective Thermolysis
The Nd:YAG laser has excellent utility for a variety of aesthetic treatments because its wavelength permits maximum energy absorption by the target (hair or lesion) with minimum absorption by the surrounding skin structures. The theory of selective photothermolysis states that by optimizing certain application parameters, the practitioner can target a specific chromophore for destruction while minimizing the damaging effects on the surrounding tissue. The main skin components that absorb laser radiation are water, melanin, and oxyhemoglobin.
Skin is transparent to laser radiation in the 600- to 1100-nm range—the range in which the dark brown-to-black pigment melanin is the most attractive target for the laser energy. Absorption of radiation by melanin decreases as the wavelength increases and is relatively weak at the upper end of the range. Epidermal melanin content limits the depth of penetration and energy fluence that can be used without unacceptable thermal injury to the skin. Shorter-wavelength radiation is better absorbed by melanin, but it does not penetrate deeply into skin; thus, shorter-wavelength lasers are most effective in patients with darker hair and lighter skin.
Conversely, longer-wavelength lasers penetrate the skin more deeply, are not strongly absorbed by epidermal melanin, and cause little skin reaction. However, higher energy fluences are needed to deliver sufficient energy for effective treatment of the hair or lesion. In practice, longer-wavelength lasers are safer for patients with darker skin, but, in any case, energy can be delivered to the hair follicles only if there is more melanin in the hair than in the skin; the hair must be darker than the skin.
With most medical lasers, the practitioner is able to adjust the power setting and duration of the laser pulse. As a general rule, the length of the pulse is as important as the wavelength or the power setting in determining its medical use. Lasers can be operated in continuous wave (CW) or pulsed modes. CW lasers emit a steady beam for as long as the laser medium is excited. Pulsed lasers emit radiation in individual pulses, which may be long (thousandths of a second) or short (millionths of a second).
Q-switching allows the laser to store energy between pulses, enabling a higher power output. The control of pulse duration permits a broad spectrum of lesions to be treated in a customized fashion. For example, the Q-switched Nd:YAG laser is effective for removing tattoo ink and vascular lesions, but gives only fair results for hair removal. Millisecond-range, long-pulsed Nd:YAG laser radiation is very effective for permanent hair removal and spider-vein treatment.
The optimum pulse duration should be shorter than the thermal relaxation time of the epidermis, allowing heat energy to be dissipated, but longer than the thermal relaxation time of the target chromophore (hair or vessel), confining the heat to that structure. This process is facilitated by cooling the skin, leaving the deeper hair follicles more vulnerable to treatment, and by having longer pulses that enhance the heating and expand the zone of thermal damage to the target.
Some cooling methods used by Nd:YAG lasers include cryogen sprays, cooling gels, contact cooling using a chilled apparatus that is placed in direct contact with the skin, and cold airflow over the treatment area.
Uses of the Nd:YAG
Permanent hair reduction. Before the advent of longer-wavelength lasers, longer pulse durations, and more efficient cooling devices, laser-assisted hair removal was best suited for Fitzpatrick phenotypes I–III2 with dark terminal hairs. By using conservative fluences, longer pulse durations, and multiple treatments, the long-wavelength Nd:YAG laser can safely and effectively re-move hair in darker skin types.
Several long-pulsed Nd:YAG lasers have recently been approved by the US Food and Drug Administration (FDA) for permanent hair removal in all skin types (Fitzpatrick I–VI), including tanned skin.3 Compared to other lasers, the Nd:YAG laser may be less efficacious for treating lighter phenotypes, because there is less absorption by melanin at the 1064-nm wavelength. However, this phenomenon allows the Nd:YAG laser to work effectively on darker and tanned skin types, Fitzpatrick III–VI.
If traditional laser devices are used on darker phenotypes, burning or hypopigmentation may result. With the Nd:YAG laser, all skin types—including dark-skinned and tanned patients—can be treated safely.
Pseudofolliculitis barbae. Long-pulsed Nd:YAG lasers have been used clinically since 1999 to effectively and safely treat pseudofolliculitis barbae (PFB), commonly known as shaving bumps. PFB is a widespread problem among individuals with curly hair and darker skin. As the hair follicle grows out of the skin, it immediately curls and re-enters the skin. The skin reacts to the hair as a foreign body and be-comes inflamed and irritated, creating bumps. Over time, this can cause scarring in beard and neck areas.
In the past, the only workable way to “treat” this condition was simply to grow a beard. The Nd:YAG laser can provide long-lasting, effective relief from PFB by removing the hair follicles, and it is cleared by the FDA for this use on all skin types. It can be safely and effectively used on tanned or dark-skinned patients, with no pigment changes in the neck or facial skin.
Vascular lesions. Currently, only long-pulsed Nd:YAG lasers can compete with the two traditional vein-treatment techniques: sclerotherapy for superficial telangiectasias and surgery for deep varicose veins. Laser treatment gives patients another option, and avoids the adverse side effects inherent in the other therapeutic methods.
The Nd:YAG laser can be used for photocoagulation and hemostasis of a variety of vascular lesions, including port wine stains, hemangiomas, telangiectasias, rosacea, Venus lake leg veins, and spider veins. The 1064-nm wavelength is absorbed well by hemoglobin and penetrates the skin deeply. Minimal melanin absorption allows such systems to treat patients of all phenotypes.
The laser radiation is selectively absorbed by oxyhemoglobin in the target vessel and converted to heat energy, thus raising the blood temperature to the point of coagulation. This induces local blockage of the target vessel with minimal effect on the surrounding tissue.
Excessive leg veins are the main concern for the majority of patients with vascular lesions. Short wavelengths can be used to treat superficial telangiectasias on the legs, but they cannot eradicate deeper reticular veins, which are actually the cause of 90% of leg telangiectasia cases. Most patients want to remove veins of all sizes and depths; because Nd:YAG laser settings—fluence, pulse duration, and pulse repetition rate—can be adjusted throughout wide ranges, this laser is an excellent choice for efficiently treating both superficial and deeper vessels.
Applying Nd:YAG lasers to larger leg veins (up to 3 mm) requires higher fluences and longer pulse lengths. Smaller facial veins are better treated with shorter pulse durations at higher fluence settings. Side effects include transient redness, moderate hyperemia, and mild edema when the treatment is performed on the whole face.
These effects are usually not observed with treatment of local vascular lesions (spider hemangiomas or separate telangiectasias). This means that the patients return to their normal lifestyle immediately after the procedure. After laser treatment of vascular lesions of the leg, transient edema at the target site and mild hyperpigmentation where large vessels were removed may occur. However, these effects resolve within several weeks.
Benign pigmented lesions. The Q-switched Nd:YAG laser produces a 1064-nm-wavelength beam with a pulse duration of 10 nanoseconds. Melanin does not absorb the 1064-nm wavelength well, so this wavelength is not ideal for treating many benign superficial pigmented lesions. However, despite lower melanin absorption relative to other lasers, the advantage of the Nd:YAG lies in its ability to penetrate more deeply into the skin (up to 4–6 mm). The Q-switched laser can be highly effective for epidermal and dermal pigmented lesions, especially those with a vascular component, including Ota’s nevi, cafe au lait macules, and lentigines (age spots). Again, this laser is useful for treating lesions in people with darker skin tones.
Tattoos. Nd:YAG laser technology has improved the method for removing tattoos with minimal scarring.4 In the past, tattoos could be removed by carbon dioxide laser therapy after vaporizing the epidermis and superficial dermis. Although effective, this treatment has a high incidence of scarring and pigment disturbance. The Q-Switched Nd:YAG laser, using high energy delivered in ultrashort pulses, offers improvement in treating tattoos, particularly black and blue-black “amateur” tattoos. When the laser is directed toward a specific area of the tattoo, the ink particles are broken up by the laser, then subsequently absorbed and removed by the body’s own filtering system.
Red pigmentation in scars. Unsightly scars are often the only reminder of a previous surgery or traumatic wound. When the aesthetic issue is color mismatch with the surrounding skin as a result of hypervascularity, it can be addressed with the Nd:YAG laser. Some degree of epidermal tightening can be achieved with the Nd:YAG laser, which can also be useful for atrophic scars.
When the redness is caused by inflammatory or postinflammatory changes, it may fade naturally in up to 18 months if adequately protected from exposure to ultraviolet radiation. But mature hypervascular scars have little or no chance of improving spontaneously. Selective photo-thermolysis with a long-pulsed frequency-doubled Nd:YAG laser can be used to eliminate the unsightly vascular components of mature scars. The color and texture of scars is often improved by this technique.
The Newest ‘Wrinkle’
Photorejuvenation using the Nd:YAG laser is an exciting new procedure designed to produce younger- and healthier-looking skin. As we age, we begin to see visible signs of damage appearing in our complexions, such as wrinkles, freckles, broken capillaries, dark spots, blotchy skin color, enlarged pore size, and sun damage.
Collagen is a key protein in the connective tissue infrastructure of healthy skin. Aging, sun damage, and smoking break down the collagen support layers, leading to wrinkles and the other indications of aging.
Treatment with the Nd:YAG laser heats the underlying layers of the skin, encouraging the formation of new collagen that results in smoother, younger-looking skin. Epidermal cooling systems facilitate laser-induced dermal injury without ablating the epidermal layer. In this way, the superficial epidermis is protected with every laser pulse, providing a safe, noninvasive solution that can be tailored to individual conditions and skin types.
The theory behind this treatment is that the dermal injury stimulates the production of collagen and elastin, thereby improving skin quality. The less-efficient absorption by melanin of long-pulsed Nd: YAG laser radiation allows safer treatment of patients with all skin types. Nonablative laser techniques are well-suited for patients who request rejuvenation treatments of the aging face with little or no downtime and minimal discomfort.
Although the improvements in photodamaged skin are subtle and gradual, Nd:YAG laser photorejuvenation therapy is well-tolerated by patients with all skin types. Clinical studies have compared the skin-tightening results of Nd:YAG lasers to other commonly used radiofrequency devices. The Nd:YAG laser was found to be more effective than radiofrequency de-vices.5 In addition, the laser treatments proved to be faster, less painful, safer, and more economical for the patient and practitioner than treatments with other devices.
Laser facial rejuvenation is recommended in a series of four treatments, performed about every 4 weeks. Some patients have reported results in just a few days after treatment; however, the optimum results occur approximately 90 days after the final treatment. As the aging process takes place, and the effects of gravity cause the skin to lose its youthful appearance, treatment with the Nd:YAG laser is an excellent option for skin rejuvenation. This noninvasive treatment is becoming one of the fastest-growing trends in medical cosmetics.
In a Nutshell
The Nd:YAG laser emits radiation with a wavelength that makes it a highly versatile tool for an aesthetic practice. It is very effective for hair removal in all skin types; it treats vascular lesions, benign red-pigmented lesions, tattoos, and scars; and it is rapidly gaining popularity as a nonablative photorejuvenation device. PSP
Benjamin A. Bassichis, MD, is a double-board-certified facial plastic and reconstructive surgeon and the director of the Advanced Facial Plastic Surgery Center in Dallas. A renowned physician who lectures throughout the country on the latest aesthetic surgery procedures, he has been featured on prominent national news programs. He is a clinical assistant professor at the University of Texas–Southwestern Medical Center and volunteers to care for veterans at the Dallas Veterans Administration Hospital. He can be reached at (972) 774-1777 or his Web site, www.advancedfacial plastic.com.
References
1. Einstein A. On the quantum theory of radiation. Physikalische Zeitschrift. 1917;18: 121–128.
2. Fitzpatrick TB. The validity and practicality of sun-reactive skin types I through VI. Arch Dermatol. 1988;124:869–871.
3. US Food and Drug Administration. 510(k) summary of effectiveness for the Candela GentleYAG family of laser systems. Available at: http://[removed]www.fda.gov/cdrh/pdf3/k033172[/removed].pdf Accessed July 29, 2005.
4. Ehrlich M, Goldman MP. Undo those tattoos. Plastic Surgery Products. 2005;15(8): 40–44.
5. Taylor M. Comparing skin-tightening results of the GentleYAG versus a commonly used radiofrequency device. Presented at: American Society for Laser Medicine and Surgery 25th Annual Meeting, Lake Buena Vista, Fla, March 30–April 3, 2005; Lasers Surg Med Suppl. 2005;17: 1–94.
