The Q-switched Nd:YAG laser is an established modality of treatment for epidermal and dermal pigmented lesions. The dual wavelengths of 1064nm and 532nm are suited for the darker skin tones encountered in India. Though this laser has become the one of choice for conditions such as nevus of Ota, Hori's nevus and tattoos, its role in the management of melasma and other acquired dermal melanoses is not clear. Despite several studies having been done on the Q-switched Nd:YAG laser in melasma, there is no consensus on the protocol or number of sessions required. Acquired dermal melanoses are heterogenous entities with the common features of pigment incontinence and dermal melanophages resulting in greyish macular hyperpigmentation. This article reviews the current literature on laser toning in melasma and the role of the Q-switched Nd:YAG laser in stubborn pigmentary disorders such as lichen planus pigmentosus. As the pathology is primarily dermal or mixed epidermal-dermal in these conditions, the longer wavelength of 1064nm is preferred due to its deeper penetration. Generally multiple sessions are needed for successful outcomes. Low fluence Q-switched Nd:YAG laser at 1064nm utilizing the multi-pass technique with a large spot size has been suggested as a modality to treat melasma. Varying degrees of success have been reported but recurrences are common on discontinuing laser therapy. Adverse effects such as mottled hypopigmentation have been reported following laser toning; these can be minimized by using larger spot sizes of 8 to 10mm with longer intervals (2 weeks) between sessions.
Keywords: Acquired dermal melanosis; Q switched Nd:YAG laser; lichen planus pigmentosus; melasma.