LOW FLUENCE Q-SWITCHED Nd: YAG LASER TONING AND Q-SWITCHED RUBY LASER IN THE TREATMENT OF MELASMA:A COMPARATIVE SPLIT-FACE ULTRASTRUCTURAL STUDY

摘要

Background: Melasma still presents as a difficult entity to treat, especially in the Asian skin phenotype. Recently laser toning with the Q-switched Nd:YAG has attracted attention. The present study investigated the efficacy of Q-switched Nd:YAG laser toning for melasma, with a histopathological comparison with the Q-switched ruby laser.Subjects and Methods: Eight Japanese females (41-57 yr, mean 52.5 yr) with Fitzpatrick skin type III and bilateral melasma participated in the study. One half of each subject’s face (randomly chosen) was treated with Q-switched 1064 nm Nd:YAG laser toning (pulse width 5-20 ns; spot size, 6 mm diameter; fluence, 3.0 J/cm~(2), 5-7 passes, once/week, 4 weeks: QS:YAG group), and the contralateral half with a single treatment using a Q-switched ruby laser (694.5 nm, pulse width 20 ns, spot size 4 mm diameter; fluence 4.0 J/cm~(2), 1 pass with approximately 20% overlap: QS:Ruby group). Skin biopsies were taken immediately after the 4~(th) Nd:YAG session and the single ruby session, and histopathological comparison was performed with light- and transmission electron microscopy (TEM).Results: Improvement in melasma pigmentation was seen in both the QS:YAG- and QS:Ruby-treated sides, and this was well-maintained in the QS:YAG group. Ultrastructurally, melanin granules were destroyed in both groups, but there was considerably more morphological epidermal and dermal damage in the QS:Ruby specimens compared with minimal epidermal disruption and cellular damage in the QS:YAG specimens.Conclusions: Q-switched 1064 nm Nd:YAG laser toning offered superior results in the treatment of melasma in the Japanese skin type compared with the Q-switched ruby laser, both ultrastructurally with less immediately post-treatment cellular damage and macroscopically, and a longer recurrence-free interval.