Laser Surgery in Dark Skin

Tina S. Alster, MD, Elizabeth L. Tanzi, MD

In This Article

Abstract and Introduction

Although challenging, effective laser surgery in patients with darker skin tones can be achieved despite a higher inherent risk of untoward side effects. While the incidence of undesirable postoperative sequelae has decreased with the development of advanced laser technology and individualized treatment parameters, these risks may never be eliminated completely. Consequently, thorough patient preoperative preparation and education regarding the risks of cutaneous laser therapy will remain an essential component of treatment in darkly pigmented patients. In the future, as more refined laser techniques evolve, the ability to safely and effectively treat these patients will improve.

The safe and effective laser treatment of patients with darker skin tones presents a challenge to the laser surgeon and is becoming more frequently encountered as the patient population continues to increase and become more ethnically diverse. Population statistics of the United States reveal dramatically shifting demographics in the past decade. Between 1990 and 2000, Hispanics and Asians accounted for 40% of the total growth of the US population, African Americans for 12%, and non-Hispanic Caucasians for slightly over 2%.[1] In 2000, the total number of individuals in the United States with skin of color was approximately 85 million.[1] Despite the increased demand for dermatologic laser surgery by Asians, Hispanics, and African Americans, most of the current literature remains devoted to examining laser procedures performed on individuals with fair skin tones (skin phototypes I-II) and protocols have largely been defined on the basis of the more extensive clinical experience that has accumulated surrounding these patients.

Due to its unusually wide absorption spectrum ranging from 250-1200 nm, all visible-light and near-infrared dermatologic lasers currently in use can specifically target melanin. Nonspecific energy absorption by relatively large quantities of melanin in the basal layer of the epidermis can increase unintended nonspecific thermal injury and lead to a higher risk of untoward side effects including permanent dyspigmentation, textural changes, focal atrophy, and scarring in the darkly pigmented patient. Moreover, competitive absorption by epidermal melanin substantially decreases the total amount of energy reaching deeper dermal lesions, rendering it more difficult to achieve the degree of tissue destruction necessary to effect the desired clinical result. Treatment parameters, therefore, must be carefully considered when performing laser surgery on patients with darker skin phototypes.

Although difficult, effective laser therapy in patients with darker skin phototypes can be achieved,[2,3,4,5,6,7] since the absorption coefficient of melanin decreases exponentially as wavelengths increase. Illustrating this principle, epidermal melanin absorbs approximately four times as much energy when irradiated by a 694 nm ruby laser as when exposed to the 1064 nm beam generated by the neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, thus allowing greater penetration of the longer wavelength.[8] Therefore laser systems generating wavelengths that are less efficiently absorbed by endogenous melanin can often provide a greater margin of safety while still allowing the laser surgeon to achieve satisfactory results.

When determining a treatment protocol for an individual patient, power level is at least as important as the laser wavelength chosen when treating darker skin, since highly melanized skin absorbs electromagnetic energy much more efficiently than does fair skin. For example, skin phototype VI may absorb as much as 40% more energy when irradiated by a visible light laser than does class I or II skin when fluence levels and exposure duration remain constant.[9] Thus, conservative power settings (the minimal threshold fluences necessary to produce the desired tissue effect in a given individual as determined through irradiation test spots) should be employed initially to minimize the extent of collateral tissue damage. Clearly, a prudent approach to treatment is far preferable to incurring the risk of irreparable tissue destruction resulting from excessive thermal injury, even if this may necessitate multiple laser treatments in order to achieve maximal clinical results.[10]