aFlorida Hollywood Dermatology and Cosmetic Surgery Specialists, Hollywood, FL bDepartment of Dermatology and Cutaneous Surgery, Miller School of Medicine, University of Miami, Miami, FL
Chromophore: Melanin Although there is no difference in the melanocyte density between Fitzpatrick phototypes, there is certainly an increase in the number and size of melanin granules within the basal layer keratinocytes in darker-skinned individuals. This large amount of melanin within the epidermis of darker skin types competitively absorbs laser light targeted for other chromophores. Subsequently, with the broad absorption spectrum of melanin, ranging from 250 to 1200nm, greater care and diligence must be taken when using lasers on Latino skin. A selective window for targeting melanin lies between 630 and 1100 nanometers (nm), where there is desired skin penetration and preferential absorption of melanin over oxyhaemoglobin. Absorption for melanin decreases as the wavelength increases, but a longer wavelength allows deeper skin penetration. Shorter wavelengths (<600nm) damage pigmented cells with lower energy fluencies, while longer wavelengths (>600nm) penetrate deeper but need more energy to cause melanosome damage. A longer pulse duration delivers slower laser light resulting in mitigated epidermal heating. Consequently, epidermal cooling is more effective thereby reducing rapid heating and damage to the melanosomes. The calculated TRT of melanosomes is less than 1 microsecond corresponding to 250 to 1000 nanoseconds. As previously discussed, a pulse duration less than the TRT will decrease risk of damage to the melanosome.Hair Removal With the advent of lasers with longer wavelengths, longer pulse durations, and efficient cooling devices, all skin types can be treated with lasers for hair removal with reduced risk of adverse outcomes. Caution must be taken when performing laser treatments in patients with a tan, in fact, it should be avoided to prevent adverse effects as seen in Figure 5. As the provider, it is important to ensure that the handpiece is perpendicular to the skin surface and to avoid overlapping during pulses. It is also essential to confirm the cooling device to functioning properly before starting the procedure. We believe two wavelengths are generally appropriate for use in dark Latino skin, which include the Diode laser 810nm at low fluence and high repetition rate “in motion” (up to phototypes V) and Nd:YAG 1064nm (up to phototypes VI Melasma Melasma treatment is one of the most difficult and frustrating conditions to manage and unfortunately a very common condition among Latinos. The origin of hyperpigmentation can be epidermal, dermal, junctional, or a combination. A wood’s lamp can be used to determine the depth. Given melasma has a hormonal component and is essentially caused by ultraviolet light exposure, it is expected to almost always return after treating. It is important to counsel patients that treatment does not cure their melasma. We generally turn to a laser when the case is resistant to more conservative treatment, which includes topical skin lighteners including Kligman’s formula, and/or light peels, or oral tranexamic acid. In general lasers have revolutionized the treatment of dermatological disorders but its place in the management of melasma and post inflammatory hyperpigmentation (PIH) is still controversial. The QS-Nd:YAG is the most widely used laser for the treatment of melasma. Our parameter recommendation includes fluence less than 5 Joules/cm2, spot size 6 mm, and frequency of 10 Hz. Heat can exacerbate melasma, therefore a single pass should be performed on each area to be treated prior to additional passes. Specifically, up to three passes are performed, allowing the tissue to properly cool between passes. The toning procedure will utilize low fluence with a large spot size. The number of treatment sessions varies from 5 to 10 at 1-week intervals. Rebound hyperpigmentation could be due to the multiple sub threshold exposures that can stimulate melanogenesis in some areas, and/or inflammation with secondary PIH. Monthly or quarterly maintenance is performed to maintain results. The use of pulsed dye laser (PDL) for the treatment of melasma is based on the theory that skin vascularization plays an important role in the pathogenesis of melasma. Particularly, it is known that melanocytes express vascular endothelial growth factor receptors, which cause the telangiectasias. Table 2 outlines the lasers we use to treat melasma. Figure 6 depicts a Latina patient treated with two sessions with the Picosecond 1064nm laser two weeks apart. Chromophore: Water Water is the targeted chromophore in most resurfacing procedures. Ablative resurfacing creates a controlled partial-thickness damage down to the dermis, therefore use in phototypes V and VI is usually not indicated due to the risk of dyspigmentation
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