Epidermal Fluence Threshold Determination by Real-Time Melanin Measurements

BACKGROUND AND OBJECTIVE Epidermal preservation is essential during laser treatment for vascular, hair, and benign pigment dyschromias. Epidermal tolerance is determined by epidermal melanin content, fluence, pulse width, wavelength, skin cooling, and spot size. The authors' objective was to determine the maximum epidermal tolerance for the long-pulse alexandrite 755 nm and the long-pulse neodymium-doped yttrium aluminum garnet (Nd:YAG) 1064-nm lasers for varying epidermal melanin content. MATERIALS AND METHODS Skin melanin measurements were performed at the test sites with a melanin reader, and 0.5 to 1 second of refrigerated air precooled the skin. Then, alexandrite and Nd:YAG laser test spots of 5 to 18 mm were delivered in a series of ascending fluences using 5-, 20-, and 50-ms pulse widths. Skin response at 24 to 48 and 96 hours was scored from 0 to 15 varying from "no reaction" to "severe scabbing." RESULTS Alexandrite laser, mean threshold fluences increased by a factor of 1.2 increasing from 5 to 20 ms, and by a factor of 1.4 increasing from 5 to 50 ms, among subjects with a melanin index (MI) from 9 to 25 (Fitzpatrick skin phototype I-III). The Nd:YAG fluence to reach epidermal tolerance was 6X the fluence with the alexandrite laser for the same MI in subjects with MI 26 to 35. CONCLUSION Epidermal melanin measurements are quantitative and objective, therefore, improving treatment setting determination by decreasing the risk of overtreatment or undertreatment. Address correspondence and reprint requests to: Amanda Abramson Lloyd, MD, Skin & Vein Institute, 477 N. El Camino Real, Suite D304, Encinitas, CA 92024, or e-mail: abramsonmd@gmail.com Cynosure provided support and the equipment for this study. E.V. Ross has received honoraria from Cynosure. The authors have indicated no significant interest with commercial supporters. © 2018 by the American Society for Dermatologic Surgery, Inc. Published by Wolters Kluwer Health, Inc. All rights reserved.

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