Laser therapy on darker ethnic skin


Eliot F. Battle Jr , MD a,b, *
Lori M. Hobbs, MD c

 

Dermatologic Clinics
Volume 21 • Number 4 • October 2003
Copyright © 2003 W. B. Saunders Company

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* Corresponding author. Department of Dermatology, Howard University College of Medicine, 2041 Georgia Avenue, NW, Washington, DC 20060
E-mail address: drbattle@culturamed.com



The face of America is changing. It is estimated that by the year 2050, approximately half of the population will represent darker ethnic skin types (Fitzpatrick phototypes IV to VI) [1] . With this evolving diversity, physicians and skin care specialists need to expand their knowledge and comfort level in treating darker skin tones.

Laser therapy is routinely used today to treat a myriad of general and cosmetic dermatologic conditions. Most laser procedures are performed on lighter skin types (Fitzpatrick phototypes I to III) with an abundance of published literature. For whites it is a viable and often first-line treatment option for many unwanted conditions and lesions including hair, veins, wrinkles, scars, tattoos, birthmarks, moles, and vascular abnormalities.

There is a dearth of information about lasers on darker ethnic skin types. The reasons for this are numerous. First, because of the increased risk of transient and permanent side effects (eg, blistering, dyspigmentation, and scarring) the treatment of lasers on darker skin types is a true challenge to practitioners. Most of the laser practitioners, including the “laser experts,” limit their treatments to patients with lighter skin. Second, to practitioners who treat darker skin types, there are only a few dermatologic conditions that are amenable to treatment with the currently available lasers. Finally and most importantly, there has been limited laser research on darker ethnic skin types.

Despite these issues, the demand for laser procedures on ethnic skin is growing dramatically. Laser procedures on pigmented skin are a wide-open frontier that is virtually untapped. The dermatologic surgeon needs a conservative approach combined with ingenuity, sound judgment, and a clear understanding of laser optics in treating ethnic skin.

Laser optics
Lasers (Light Amplification by Stimulated Emission of Radiation) have three basic components: (1) the pumping system, (2) laser medium, and (3) optical cavity. The pumping system is the power supply. The lasing medium, which can be gaseous, liquid, or solid, determines the wavelength of the light emitted. It supplies the electrons needed for the stimulated emission of radiation. The optical cavity houses the lasing medium. It has two parallel mirrors, one of which is partially reflective allowing the laser light to escape in the form of the laser beam.

Laser light has unique physical properties. It is monochromatic (one wavelength); coherent (wave in phase: time and space); collimated (parallel travel); and bright (high intensity). Laser light must be absorbed by the target (eg, hair and veins) to have an effect.

When laser light comes in contact with the skin, it creates four possible reactions: it can be (1) reflected, (2) transmitted, (3) scattered, or (4) absorbed. For the desired clinical effect to take place the intended target must absorb the laser light. The intended target in the skin is called a chromophore. Chromophores are pigmented molecules that absorb light at different wavelengths (Fig. 1) . Melanin, hemoglobin (oxyhemoglobin), and water are the main endogenous chromophores and tattoo ink and psoralens are examples of exogenous chromophores.


Fig. 1. Absorption spectrum chart.




When a specific wavelength of laser light is absorbed by the target chromophore, the chromophore undergoes a photochemical reaction in which the absorbed laser light energy is converted to heat. If enough heat is generated, the chromophore is destroyed. When light is absorbed by the target chromophore, there is heat diffusion conducted to the surrounding tissue. This process is called thermal relaxation.

The principle of thermal relaxation time is based on the time it takes the target chromophore to cool down by 50% of its initial temperature. The thermal relaxation time is determined by the size of the target object. Larger structures lose heat slower than smaller ones. For example, the melanosome (approximately 1 μm) has a shorter thermal relaxation time in comparison with the larger size blood vessels (10 to 100 μm).

The amount of tissue damage is affected by the fluence (energy density expressed as J/cm2); pulse duration (exposure time); and the thermal relaxation time of the target. According to the theory of selective photothermolysis, by choosing the appropriate wavelength, fluence, and thermal relaxation time, the target chromophore can be thermally destroyed without causing damage to the surrounding tissue [2] .

Pigmented skin and laser light
The pertinent difference between darker ethnic skin (phototypes IV to VI) and white skin is the amount and packaging of epidermal melanin. Melanin absorbs laser light over a wide range of wavelengths. To treat dermal chromophores, light must pass through the heavily melanized epidermis. Because of the wide absorption range of melanin (250 to 1200 nm), laser light intended for deeper targets is absorbed within the pigmented epidermis. This absorbed light is converted to epidermal heat, which can create the unwanted epidermal side effects, such as blistering, dyspigmentation, and scarring. This competition of epidermal melanin absorption causes fewer laser lights to reach the intended chromophore, reducing the efficacy of lasers for persons with darker skin types when using comparable fluences.

With the advent of new-generation lasers, which use longer wavelengths, longer pulse durations, more efficient cooling devices, and a wider range of available treatment fluences, the laser surgeon can decrease the likelihood of adverse events while maintaining efficacy.

The absorption spectrum of melanin decreases as wavelengths increase. Longer wavelengths also penetrate deeper with more selective absorption of dermal-targeted chromophores and less efficient absorption of epidermal melanin. Using longer wavelengths reduces epidermal injury.

Efficient cooling devices (eg, sapphire cooled tip and cryogen spray cooling) are essential when treating darker ethnic skin types. Light absorbed by melanin in the epidermis is converted to heat and without efficient cooling this heat creates unwanted thermal injuries, including blistering, dyspigmentation, and scarring. Cooling can be performed by contact (cooling device touching the skin) or noncontact (eg, cooling the skin with a cooling spray, air, or gas). Excessive cooling is not without risk for darker ethnic skin types. Cryogen spray can reach temperatures as low as -26.2°C. Excessive cryogen spray and delay parameters can result in unwanted side effects including blistering and postinflammatory dyspigmentation.

Longer pulse durations allow for more efficient cooling of the epidermis, reducing epidermal injury. The melanin in the epidermis absorbs laser light across most of the useful photobiologic light spectrum. This absorbed epidermal light is converted to heat. Pouring the energy into the skin slower (longer pulse durations), the epidermis absorbs the light slower and heats up slower, making the cooling more efficient. Longer pulse durations also minimize direct melanosome destruction. The thermal relaxation time of melanosomes is in the nanoseconds and is directly sparred when using pulse durations in the milliseconds.

Using conservative treatment fluences is extremely important when treating darker pigmented skin. The laser surgeon needs to use the lowest possible fluence to obtain the desired clinical outcome. Multiple test spots are essential in determining the best laser parameters. These test spots should be performed on similar sun-exposed skin as the treatment site. If the treatment protocol calls for overlapping spots (eg, hair removal), then the multiple test spots should be overlapping. Waiting for the laser tissue response is imperative. Tissue response after laser application on pigmented skin may take longer to evaluate in comparison with white skin. For example, routine post–laser-induced erythema is subtle and more difficult to detect if seen at all.

The laser consultation
In treating patients with darker ethnic skin one should proceed conservatively and cautiously. Questions to be obtained during consultation include the following:

Patient's true Fitzpatrick phototype (sun exposure history, Table 1 )
Thorough past medical and surgical history
Is there a history of keloid or hypertrophic scarring?
Is there a history of trauma-induced dyspigmentation?
Patient's family ethnicity
Has the patient been on isotretinoin?
Previous cosmetic therapy treatments and results



Table 1. Fitzpatrick phototypes (skin types)
Based on the first 45 minutes of sun exposure of untanned skin the first day of spring.
Phototype Unexposed skin color Reaction
I White Always burns, never tans
II White Always burns, minimal tan
III White Burns minimally, tans gradually
IV Light brown Burns minimally, tans well
V Brown Rarely burns, tans profusely
VI Dark brown or black Never burns, tans deeply


It is crucial to explain the risks and benefits of the procedure thoroughly, including the following:

Realistic treatment results
Time for each treatment and number of expected treatments
Possible side effects and the resolution outcome of the unwanted side effects, including the postponement or cancellation of further laser treatments.
Level of discomfort or pain during and after laser treatments
The mandatory requirement to wear protective goggles
Overall cost of treatments

Vascular lesions
For lighter skin types, facial telangiectasias, port-wine stains (PWS), hemangiomas, and leg veins are commonly and successfully treated with lasers. Laser treatments for vascular lesions are relatively contraindicated in patients with darker skin types. The added concern with treating vascular lesions with lasers in darker skin tones is that wavelengths used to treat vascular lesions are strongly absorbed by epidermal melanin. Epidermal melanin absorbs the same laser light intended for hemoglobin creating the strong potential for side effects, such as permanent or transient blistering, ulceration, dyspigmentation, and scarring. Vascular lasers using longer wavelengths (eg, neodymium:yttrium-aluminum-garnet [Nd:YAG]) offer the greatest potential to treat darker ethnic skin. But with the high fluences required to treat vascular lesions successfully there is still a high potential for unwanted side effects.

The response rate of vascular lasers for the treatment of PWS varies widely in the literature. The range published is from 36.5% to 78.6% of more than 50% clearing [3] [4] . Factors that portend better clearance were found in patients who were 10 years old or younger, facial location, smaller-sized lesions, and lighter color. Variables that portend a negative response were PWS located on the distal extremities; phototypes IV and V; large lesions; older patients (≥ 50 years); and purplish color [5] .

The response rate for the treatment of PWS in pigmented skin has not been elucidated. It is presumably lower than the 36.5% to 78.6% of patients experiencing 50% clearance [4] [5] . In addition, side effects of dyspigmentation are presumably greater. Garret and Shieh [6] in their report of three African American patients, phototypes IV and V, treated two subjects with PWS and one subject with a vascular labial lesion. They used the flashlamp pulsed dye laser (PDL) (585 nm) with a 5-mm spot and fluence range 6.5 to 8 J/cm2. There was 90% to 100% clearance of one subject with PWS of the neck and one subject with a labial vascular papule. The second PWS subject was lost to follow-up. Both PWS patients experienced hypopigmentation and one experienced erosion. The treatment intervals were long, 7 to 12 months, which allowed sufficient time for the improvement of side effects before the next treatment. Postinflammatory hyperpigmentation can be a major concern. Goh et al [7] in his treatment of PWS with the PDL experienced transient hyperpigmentation in all 36 patients.

The flashlamp PDL with the longer wavelengths and deeper penetration should in theory be safer for pigmented skin. Ho et al [8] , however, in his retrospective study of 107 Asian patients with PWS compared the treatment of the PDL with the variable pulse width frequency doubled Nd:YAG 532-nm laser. He found 14% of patients experienced the complication of altered pigmentation regardless of the type of vascular laser. None of the patients had complete clearing. Twenty-three percent of patients experienced clearing of more than 50%. The average number of treatments was six.

In comparing cooling versus noncooling devices with the PDL, Chang and Nelson [9] found cryogen spray cooling was important in decreasing side effects and increasing efficacy. They found higher fluences could be used with the addition of cryogen spray cooling.

Two years later, Chang et al [10] compared cryogen spray cooling at 585 nm versus 595 nm in his retrospective study of 64 Asian patients with PWS. The pulse duration of 1.5 millisecond, 7 mm spot, and fluences in the range of 7 to 10 J/cm2 were held constant. Treatments ranged from one to six in his study. His group reported a statistically significant improvement with the 585 nm postulating that at this wavelength the absorption coefficient of blood is higher. There was no permanent hypopigmentation or scarring. Transient hyperpigmentation was noted in both groups with 43.7% in the 585-nm group and 37.5% in the 595-nm group.

Although Chang et al [10] experienced more improvement with the 585 nm, there was slightly higher percentage of transient hyperpigmentation. Longer wavelength (595 nm) PDL lasers are favored by the authors. Cryogen spray cooling is imperative to help protect the epidermis. It is suggested that test spots be done to determine the appropriate fluence. Lower fluences are favored for the initial treatment with increasing fluences as determined by the clinical outcome. Multiple treatments on average are more numerous than those typically seen in phototypes I to III. Partial clearing is generally normal. Most patients experience a cosmetic improvement.


Leg telangiectasias
The success of laser therapy of leg veins has improved dramatically over the past few years, particularly with the use of the longer wavelength Nd:YAG laser systems. Sclerotherapy remains the gold standard for the treatment of leg veins [11] . Lasers are an option based on the practitioner's comfort level and the patient's willingness for an alternative therapeutic modality. Lasers are chosen over sclerotherapy for a number of reasons, including patients who are needle phobic, patients in which sclerotherapy was not successful, and for those patients in which there is postsclerotherapy matting.

Combining the fact that epidermal melanin competes for the laser light used to treat vascular lesions and the high fluence requirement for these lasers to be successful, the treatment of leg veins is an undesirable option for most patients with darker ethnic skin. The lasers most promising are the long-pulse Nd:YAG systems. Currently, there are no reports in the literature of these lasers for the treatment of leg veins on darker ethnic skin.

Lasers for pigmented lesions
Patients of darker skin tones have great concerns with altered skin pigmentation. Patients frequently seek laser consultations for the treatment of melasma, postinflammatory dyspigmentation, lentigines, dermatosis papulosis nigra, nevus of Ota, and tattoo removal. Some of these conditions can be treated with lasers, whereas others are best treated with conventional therapies.

Melasma is a commonly acquired hypermelanosis that occurs most frequently on the face in women. Q-switched lasers for the treatment of melasma, particularly the Q-switched ruby, have been attempted, although unsuccessfully [12] . Histologically, the laser produces immediate rupture of the melanosomes with fluence-related injury to the pigment-containing cells found in the epidermis and dermis. This pigment incontinence and repackaging may contribute to the refractory nature of laser-treated melasma [12] . Pigmentary alteration is a common side effect.

The erbium:YAG laser has been evaluated for the treatment of melasma. Manaloto and Alster [13] resurfaced 10 female patients, phototypes II to V. All patients showed improvement and all experienced postinflammatory hyperpigmentation. The authors concluded the erbium:YAG laser should be considered only for refractory melasma. Additionally, Nouri et al [14] in a small series of four patients, phototypes IV to VI, compared the pulsed carbon-dioxide laser with the pulsed carbon-dioxide followed by the Q-switched alexandrite. The combination treatment group was designed to treat the epidermal and the dermal component of melasma. Complete resolution was seen in the combination group. In the carbon-dioxide treatment group alone, there was peripheral hyperpigmentation seen at the 4- to 6-week follow-up. Nouri et al [14] theorized that in the carbon-dioxide treatment group, the low energy used at the edges where there were intact melanocytes was enough cutaneous injury to cause postinflammatory hyperpigmentation, especially for persons with an underlying aberrant melanocytic disorder. Future potential laser treatments for melasma may be in the dual therapeutic approach as indicated by this small pilot study. Nevertheless, conventional therapies are recommended and remain the gold standard for the treatment of melasma for all skin types, especially pigmented skin.

The self-limiting disorder of postinflammatory hyperpigmentation is distressful to most persons of color. The postinflammatory changes may be superficial or deep. For similar reasons with melasma, Q-switched lasers are not effective [12] . Because of the risk of pigmentary alteration with laser treatments and the self-limiting nature of this disorder, conventional therapies are favored.

Lentigines are a sign of aging and photodamage for most persons of color, especially Asians. Q-switched lasers are effective for treating lentigines. The commonly used Q-switched systems are the Q-switched ruby (694 nm, 25 ns); Q-switched alexandrite (755 nm, 100 millisecond); and frequency-doubled Q-switched Nd:YAG (532 nm). All produce immediate whitening and subsequent crusting at the treated sites, which typically lasts 7 to 14 days. Postinflammatory altered pigmentation is transient and often ensues lasting up to a few months. Murphy and Huang [15] report postinflammatory changes in up to 25% of Asian patients using the Q-switched ruby. Jang et al [16] noted postinflammatory hyperpigmentation in 4% and postinflammatory hypopigmentation in 1% of his Asian patients using the Q-switched alexandrite.

Lentigines often are eradicated with the Q-switched lasers in one to two treatments. The published rates of postinflammatory changes are lower than what the authors have experienced in treating pigmented skin with the Q-switched laser systems. Transient hyperpigmentation is the most common side effect ranging from 35% to 50% of patients.

The intense pulsed light sources are helpful to reduce lentigines. Unlike the Q-switched systems, multiple treatments are necessary and side effects of pigmentary alterations are less common [17] . To the authors' knowledge, there are no published reports of the use of intense pulsed light sources in the treatment of lentigines in phototypes IV to VI.

Dermatosis papulosis nigra can be treated with the 532-nm frequency-doubled Q-switched lasers. The lowest fluence to obtain the desired popping sound (when the tissue becomes plasmoid) is the therapeutic end point in which the lesion should look darker in color. Lesions usually respond after one to two treatments. The spot size should cover the lesion completely to avoid surrounding postinflammatory changes. When the appropriate fluence is used, the risk of postinflammatory changes is low. Spoor [18] treated 34 patients (88% African American, 6% Asian, and 6% Hispanic) using the 532-nm diode laser. He obtained clearing after one treatment in 90% of patients. As expected, the treated sites hyperpigmented and sloughed off over a 3-week period. Only one patient experienced transient hypopigmentation. It is the opinion of the authors that light electrodessication is preferable, just as effective, and financially more affordable.

Nevus of Ota is a rare dermal melanocytic lesion. It is commonly seen in Asians affecting, 0.6% of the Asian population [19] . It is less common in African Americans. Q-switched lasers, ruby, alexandrite, and 1064-nm Nd:YAG have been used to treat nevus of Ota with adverse events of pigmentary alteration, textural irregularities, and scarring occurring infrequently. Multiple treatments are necessary and can be performed as early as every 2 to 3 months. From observation, it seems that longer duration between treatments provides a decrease in the total number treatments necessary over time.

The Q-switched systems seem to lighten the nevus of Ota through an initial neutrophilic inflammatory response and a subsequent removal of melanin by the laser affected melanosomes that are removed by macrophages to the regional lymph nodes [20] [21] . In addition, unlike the Q-switched ruby and alexandrite, the Q-switched Nd:YAG with its tissue splattering may allow further removal of melanin by transepidermal elimination [22] .

The Q-switched ruby laser, the first developed Q-switched laser, was reported early in the literature to work well for nevus of Ota [23] [24] . Watanabe and Takahashi [21] found on average it required three to four treatments, 3 to 4 months apart, to achieve a good response of 40% to 69% improvement in over half of the patients treated. Multiple treatments increased the response rate. Transient hyperpigmentation and few side effects were observed. In the literature, the percentage of transient altered pigmentation with the Q-switched laser on pigmented skin varies with transient postinflammatory hyperpigmentation seen most commonly [21] [24] [25] . In a large retrospective study of 101 patients treated with the Q-switched ruby laser hypopigmentation was seen in 16.8% of patients and hyperpigmentation in 5.9% of patients 1 year after the last laser treatment [25] . Nevertheless, as seen by these studies, the complication rate is low.

Chan et al [22] did a side-by-side comparison study of the Q-switched alexandrite and Q-switched Nd:YAG for the treatment of nevus of Ota. His group found that the Q-switched alexandrite treatment was more tolerable, but the Q-switched Nd:YAG was more effective in lightening the nevus of Ota after three or more treatments at 3- to 9-month intervals. In comparing the Q-switched ruby with the Q-switched Nd:YAG after one treatment at 1 month follow-up for 20 patients, Ts et al [26] showed a slight improvement with the Q-switched ruby. In general, all Q-switched laser systems work well on phototypes IV to V, with lighter-skinned individuals cosmetically faring better with shorter wavelengths (Q-switched ruby) and darker-skinned individuals faring better with the slightly longer wavelengths (Q-switched alexandrite and Q-switched Nd:YAG). It is the opinion of the authors that, depending on the phototype, the use of the Q-switched ruby is preferable for the treatment of nevus of Ota.

For the treatment of nevus of Ota in African Americans, phototype VI, however, the laser of choice is the Q-switched 1064-nm Nd:YAG. To the authors' knowledge, there are no reports in the literature to suggest the exact response rate. It is presumably lower, however, compared with their Asian counterparts. This is because of the competition by epidermal melanin hindering the absorption of laser light to the pigmented dermal cells.

Recurrence of nevus of Ota has been reported. Rates in the literature range from 0.6% to 1.2% [27] . The exact mechanism is unclear. It is unknown if the recurrence of nevus of Ota is laser dependent or caused by incomplete clearance leading to reactivation. Weider et al [28] in his long-term follow-up of 27 patients treated with the Q-switched ruby laser showed a 50% clearance after four treatment sessions. On follow-up 4 years later, there was no relapse or recurrence. In evaluating the Q-switched Nd:YAG laser, Kunachak and Leelaudomlipi's [29] prospective study of 68 patients with acquired bilateral nevus of Ota–like maculae, characterized by dermal hyperpigmentation with dendritic melanocytes within the dermis, underwent two to five treatments with 100% clearance. On follow-up at a mean duration of 42 months, there was persistent clearance. Nevertheless, periodic follow-up and informing the patient of the remote possibility of recurrence are prudent.


Tattoos
The initial adornment of tattoos for some persons fades to an undesirable image prompting patients to seek removal. For persons of pigmented skin, laser tattoo removal is the treatment of choice. Surgical modalities, salabrasion, microsanding, and retattooing are fraught with various side effects of scarring, textural irregularities, hyperpigmentation, or hypopigmentation.

The Q-switched Nd:YAG is an excellent choice of therapy for persons of color [30] . Compared with the Q-switched alexandrite and Q-switched ruby, there is less risk of hyperpigmentation and permanent hypopigmentation. The longer wavelength (1064 nm) has less competition with epidermal melanin than the other Q-switched devices.

The Q-switched Nd:YAG is perfect for dark tattoo inks (blue and black). Brighter colors like teal and purple are best treated with the Q-switched alexandrite, but there is a greater risk of hypopigmentation (Fig. 2) . Red is best treated with the 532-nm Q-switched Nd:YAG. On pigmented skin, the 532 nm has a great risk of transient or even permanent hypopigmentation because of the strong competition with melanin.


Fig. 2. Tribal tattoo on the back with a teal color plant extract. Treated first with Q-switched Nd:YAG unsuccessfully. The 755-nm alexandrite in efforts to rid the teal color resulted in clearing most of the tattoo color; however, postinflammatory hypopigmentation resulted.




Multiple treatments are necessary. On average, 8 to 12 treatments may be required with a minimum of 6 to 8 weeks between sessions with longer durations acceptable. Amateur tattoos require less number of treatments than professional tattoos [31] . There is rarely 100% clearing. Most tattoos clear to a point of being cosmetically acceptable. For large multicolored decorative tattoos on darker skin, however, some brighter color inks may not clear well because of a great chance of hypopigmentation. It is advisable to discuss with these patients that there will be incomplete laser tattoo removal in which the treated outcome may appear worse than the original decorative tattoo.

Side effects of laser tattoo removal on pigmented skin are transient and rarely permanent hyperpigmentation, hypopigmentation, and scarring. These side effects can generally be avoided by starting at low fluences on the initial visit. The typical initial setting for a phototype V patient with the Q-switched Nd:YAG is a spot size of 3 mm and fluence of 3.6 or 3.8 J/cm2; for phototype VI a 3 mm spot size and a starting fluence of 3.4 to 3.6 J/cm2 (Fig. 3) . With additional treatments, fluences are adjusted upward to accommodate for the clearing of pigment (or less amount of chromophore). Initial whitening and subsequent crusting are typically seen, which resolves over 2 weeks. Tissue splattering and pinpoint bleeding are seen with the smaller spot size of 2 mm. Edema and erythema can be seen and last for a few hours if present.


Fig. 3. Eight weeks after a test spot to the letter “O” with the Q-switched Nd:YAG. Good clearance noted at test spot compared with the nontreated site. A 3-mm test spot, 3.8 J/cm2.




Intense pulsed light sources provide promise for tattoo removal in pigmented skin. To date, however, there are no specific reports on its use on pigmented skin.

Skin rejuvenation
Nonablative devices are desirable therapeutic options for skin rejuvenation of darker phototypes. Ablative lasers have been used infrequently on darker-skinned individuals, but the increased risk of transient and permanent dyspigmentation and scarring renders it impractical for most ethnic patients. These potential risks outweigh the benefits. It is not recommended to use the carbon-dioxide laser for resurfacing in the darker phototypes. Although the erbium:YAG laser seems safer than using the carbon-dioxide laser because of less collateral thermal conduction, there are still risks of transient hyperpigmentation, scarring, and permanent hypopigmentation. The ablative resurfacing procedure routinely should be discouraged even in the most refractory and severe cases.

Ho et al [32] in his study of 25 patients (Asian and Hispanic) did not resurface phototype VI, but phototypes III to V. His group used the ultrapulse carbon-dioxide laser for rhytides and acne scarring. Patients were pretreated with tretinoin, hydroquinone, and desonide. His response rate was 50% improvement for rhytides and 25% improvement for acne scarring. Postinflammatory hyperpigmentation occurred lasting 3 to 4 months. No postinflammatory hypopigmentation or scarring was seen. It should be noted, however, that only those subjects who did not show prolonged erythema, hyperpigmentation, and hypopigmentation on the test spot areas were recruited into the study.

Polnikorn et al [33] resurfaced 50 Asian patients, phototypes III to V, with the erbium:YAG laser for rhytides, acne scars, and a variety of other disorders. His group reported 80% improvement of rhytides, and 50% to 60% improvement of acne scarring. Postinflammatory altered pigmentation was seen in 30% lasting 4 to 8 weeks, with the exception of one patient lasting 4 months. Transient hypopigmentation lasting 2 months occurred in one patient.

Single-pass carbon-dioxide or erbium:YAG laser has been performed to help reduce the risks associated with multiple-pass carbon-dioxide, erbium:YAG, or combination technique of laser resurfacing. Esparza and Gomez [34] resurfaced 15 patients with one-pass carbon-dioxide technique. The results yielded a more natural look using a less aggressive technique. In this study, the patients phototypes were not mentioned [34] . Nevertheless, Esparza and Lupton [35] advocate in resurfacing ethnic skin types that using predictable techniques, avoiding aggressive resurfacing (ie, one pass, decrease trauma removing desiccated tissue), and close postoperative care leads to a successful outcome. In general, the use of ablative lasers regardless of multiple- or single-pass technique routinely should be discouraged.

Nonablative techniques are more suitable for phototypes IV to VI. More research is necessary to access the efficacy and safety on pigmented skin. Nonablative techniques are helpful in the treatment of mild to slightly moderate rhytides, acne scarring, pigmentary changes, and hair removal. Improvement of skin turgor and rhytides occurs through collagen remodeling without epidermal ablation.

Laser-assisted hair removal
Before the use of longer wavelengths and pulse durations, laser hair removal was limited to patients with fair skin and dark coarse hair. Recent advancements in hair removal lasers have produced numerous lasers approved by the Food and Drug Administration that can treat all skin types safely and effectively, regardless of skin color and ethnicity.

For laser-assisted hair removal devices to meet the Food and Drug Administration “permanent hair reduction” requirements they must show a 30% decrease of hair growth 3 months after a single treatment [36] . Most patients are not concerned with the Food and Drug Administration definition, but simply want permanent hair loss. To achieve a more permanent decrease of unwanted hairs, multiple treatments are necessary.

The diode and Nd:YAG lasers are the most suitable wavelengths to treat darker skin types (phototypes IV to VI). Based on research performed by Battle et al [37] it was reported that the 800-nm diode laser when combined with very long pulse durations and aggressive skin cooling could treat darker skin types (up to skin type VI) safely and effectively. Alster et al [38] reported that they were able to achieve a greater than 50% reduction of facial hair 6 months after treatment with a long-pulsed Nd:YAG laser in skin types V and VI. Longer wavelengths penetrate deeper into the skin increasing the ratio of dermal to epidermal heating, causing increased epidermal sparring [39] .

The diode lasers (800 nm wavelength) need to use very long pulse durations (> 100 millisecond) and aggressive skin cooling to treat darker skin types (phototype IV and V). Aggressive adjunct cooling should be used to treat patients with skin type VI safely with diode lasers [Figs. 4 and 5].


Fig. 4. Female (skin type I) before laser hair removal.





Fig. 5. Three months after three treatments with diode laser at 100-ms pulse duration and 25 J/cm2.




The Nd:YAG lasers (1064-nm wavelength) are the safest to treat darker skin types and when combined with long pulse durations (> 30 millisecond) and aggressive skin cooling can safely treat skin type VI. Combining this wavelength, with long pulse durations and aggressive skin cooling, any skin phototype regardless of skin color or ethnicity can be safely treated [Figs. 6 and 7].


Fig. 6. Female (skin type V) before laser hair removal.





Fig. 7. Four months after three treatments with Nd:YAG laser at 40-ms pulse duration and 40 J/cm2.




Miscellaneous

Keloids and hypertrophic scars
Keloids are characterized by disfiguring scars that extend beyond the borders of the initial injury, unlike hypertrophic scars, which are confined within the borders of injury. It results in the exaggerated proliferation of dermal tissue following cutaneous injury. African Americans are the most commonly affected. Patients often complain about the displeasing cosmetic appearance, pain, and pruritus.

There is no effective treatment for keloids. Surgical modalities offer a temporary improvement; however, the chance of recurrence is high. Intralesional steroid injections, interferon, radiation therapy, silicone dressings, and PDL lasers are common treatment modalities offered.

Keloids or hypertrophic scars should not be vaporized using the carbon-dioxide laser or any other ablative technique because of the risk of recurrence or exacerbation. PDL with its known histologic remodeling of collagen is the laser of choice for both keloids and hypertrophic scarring. The PDL is effective in reducing erythema, decreasing symptomatology, decreasing size, and improving pliability [40] [41] . By selectively targeting the vascularity of the scar, there is decreased blood supply to the growing aberrant fibroblasts within the keloidal tissue. Collagen remodeling can then ensue creating a softer, less erythematous keloid or hypertrophic scar.

The PDL can be used in combination with other treatment modalities. Connell and Harland [42] in a pilot study of 10 patients used the PDL in combination with intralesional steroids. Seven patients were noted to have 60% improvement of height; 40% improvement of erythema; and 75% improvement of symptoms, most notably pain and pruritus. Three patients had no benefit. They suggested that by pretreating with PDL, the scar tissue becomes edematous and softer, which facilitates the steroid injection [42] .

In comparing the intralesional steroids, 5-fluorouracil, 5-fluorouracil and intralesional steroid, and PDL alone the overall results were equivocal [43] . The PDL-treated group was noted to have statistically significant decreased height of scars. Multiple treatments were necessary. In patients of darker phototypes, there was an improvement of scar height with no side effects noted. Although Manuskiatti et al [43] demonstrated no statistically significant difference with fluences used, a trend toward using lower fluences showed a slightly better response. Multiple treatments were necessary every month for 6 months.

For the treatment of keloids and hypertrophic scars in darker-skinned individuals, the PDL can be used to decrease erythema, improve symptomatology and pliability, and decrease size. Lower fluences are preferred secondary to the competition of melanin with hemoglobin. Multiple treatments are necessary. A combination approach should be considered.

Summary
Like all medical procedures laser therapy comes with inherent risks and complications. Because of the increased risk in epidermal side effects when performing laser therapy on patients with darker skin, a higher level of laser expertise and clinical experience in treating darker ethnic skin is recommended to ensure that patients are treated safely. Test spots should always be done as an aid to selecting safe and efficacious treatment parameters. Because of the limited experience in treating patients with darker skin a conservative approach should always be used. Unfortunately, there are no national policies establishing credentialing requirements for those planning to practice laser surgery. The US Food and Drug Administration are responsible for granting individual laser manufacturers' permission to market their lasers for specific indications. The Food and Drug Administration also recommends operator training to use these lasers, but credentialing is a state function and consequently standards for laser therapy vary greatly from state to state. Until the bar is raised and national credentialing polices on laser therapy are established clinicians must police themselves and fully be aware of their capabilities and limitations to ensure that all patients regardless of skin color or ethnicity receive safe and effective treatments.

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Adnan Alabdulkarim, MD