Effect of Wavelength on Cutaneous Pigment Using Pulsed Irradiation.

Abstract

Several reports have been published over the last two decades describing the successful removal of benign cutaneous pigmented lesions such as lentigines, café au lait macules' nevi, nevus of Ota, and lentigo maligna by a variety of lasers such as the excimer (351 nm), argon (488,514 nm), ruby (694 nm), Nd:YAG (1060 nm), and CO2 (10,600 nm). Laser treatment has been applied to lesions with a range of pigment depths from superficial lentigines in the epidermis to the nevus of Ota in the reticular dermis. Widely divergent laser parameters of wavelength, pulse duration, energy density, and spotsizes have been used, but the laser parameters used to treat this range of lesions have been arbitrary, with little effort focused on defining optimal laser parameters for removal of each type. In this study, miniature black pig skin was exposed to five wavelengths (504, 590, 694, 720, and 750 nm) covering the absorption spectrum of melanin. At each wavelength, a range of energy densities was examined. Skin biopsies taken from laser-exposed sites were examined histologically in an attempt to establish whether optimal laser parameters exist for destroying pigment cells in skin. Of the five wavelengths examined, 504 nm produced the most pigment specific injury; this specificity being maintained even at the highest energy density of 7.0 J/cm2. Thus, for the destruction of melanin-containing cells in the epidermal compartment, 504 nm wavelength appears optimal.

A comparison of Q-switched alexandrite laser and intense pulsed light for the treatment of freckles and lentigines in Asian persons: A randomized, physician-blinded, split-face comparative trial

“…6,7 However, certain side effects, especially postinflammatory hyperpigmentation (PIH), are common in Asian people after laser therapy. 8 Double-frequency QS Nd:YAG laser with a 532-nm wavelength is appropriate for destructing melanin-containing cells in the epidermis, 9 although its use is associated with higher risk of PIH compared with QSRL and QSAL. 6 Intense pulsed light (IPL) is a noncoherent, broadspectrum light that allows variations in pulse length, mode, delay between pulses, and fluence.…”

Der gütegeschaltete Rubinlaser in der Dermatotherapie

“…Licht des Rubinlasers dringt relativ tief in die Haut ein und wird besonders von pigmentreichen Strukturen der Epidermis und Dermis -Melanin, Melanosomen, Melanozyten [20,42,54,58,69] und exogen eingebrachten Farbpigmenten -absorbiert. Durch die extrem schnelle Aufheizung der Zielstruktur kommt es zu einer selektiven Zerstö-rung, wobei diese entweder als Folge des extremen Temperaturgradienten innerhalb der Zielstruktur und/oder aufgrund der Schockwelle/Kavitation bei schneller thermaler Expansion entsteht [8,42].…”

“…Eine selektive Wirkung bei vaskulären Veränderungen kann eingeschränkt mit dem Argonlaser und v.a. mit dem blitzlampengepumpten, gepulsten Farbstofflaser (FPDL, "flashlamppumped-pulsed-dye-laser") erreicht werden [69]. Das Licht des gütegeschalteten Rubinlasers (694 nm) dringt relativ tief in die Haut ein und wird selektiv von dunklen Strukturen -Melanin und exogen eingebrachten Pigmenten -absorbiert und ermöglicht somit die Behandlung von kutanen pigmentierten Hautveränderungen und Tätowierungen.…”

Pulse duration effects on cutaneous pigment

“…This principle of localizing the energy to specific targets in the laser exposed field relies upon the combination of laser parameters of wavelength, pulse duration, fluence and spotsize. The effect of one of these laser parameters, wavelength, on melanin pigment has previously been reported [3]. In this study, it was demonstrated that of the five (504,590,694,720,760 nm) wavelengths tested, 504 nm appeared most effective and least problematic for selectively eliminating cutaneous pigment [31.…”

“…Dermal pigment is abnormal and many etiologies are responsible for its presence. One such cause, which is of significance here, is pigmentary incontinence resulting from laser irradiation [3]. Therefore, of concern when defining "optimal" parameters for selectively destroying the abnormal pigment in cutaneous pigmented lesions is the need to minimize pigmentary incontinence and prevent melanin granules from being deposited in dermal tissues.…”