Comparison of the efficacy and safety of a picosecond frequency-doubled 532-nm Nd:YAG Laser and a Q-switched frequency-doubled 532-nm Nd:YAG Laser for the treatment of ephelides: A randomized, split-lesion, double-center, controlledtrial.

Abstract

Ephelides are brown, dotted pigmentation spots that commonly appear on the face. In recent years, picosecond lasers have been increasingly used in clinical practice. Picosecond frequency-doubled 532-nm Nd:YAG lasers (PSNYLs) have been successfully used for treating several common pigmentary disorders among populations with a darker skin type (Fitzpatrick skin-type III-VI).1-3 However, a prospective study with large samples directly comparing lasers with the same wavelength but different pulse widths (PSNYL and its Q-switched counterpart, QSNYL) is lacking. The present study aimed to evaluate the efficacy and safety of PSNYL in comparison with QSNYL for treating ephelides in a split-face manner and determine whether a shorter pulse width is suitable for the treatment of pigmentation disorders. This double-center, prospective, randomized, evaluator-blinded, split-face controlled trial was approved by the Ethics Committee. Two laser devices were used in this study: a PSNYL (Picoway, Candela) and a QSNYL (Medlite C6, Cynosure). The treatment parameters were selected according to each participant's Fitzpatrick skin type, clinical presentation, and endpoint response. The right and left sides of the face were randomly assigned to the QSNYL group and PSNYL group. Standardized clinical photographs were taken for each participant using a VISIA Complexion Analysis System (Canfield Imaging Systems). The photographs were taken before treatment as the baseline and at the 1-week, 4-week, and 3-month follow-up. A blinded evaluation was conducted by three dermatologists. The primary efficacy was defined as the lesion clearance rate at the 3-month follow-up after treatment completion. The lesion clearance rate at the time of evaluation was defined as (number of lesion counts pretreatment−number of lesion counts post-treatment)/number of lesion counts pretreatment × 100%. Seventy-eight participants (74 females and 4 males) were included in this study, and all participants completed the treatment and follow-ups (Table 1). The average clearance rates were 0.773 ± 0.087 and 0.756 ± 0.103 for the PSNYL and QSNYL groups, respectively, with a significant statistical difference between the groups (Z = −2.004; p < 0.05). The photographs before and after treatment are shown in Figure 1. Average VAS scores for the PSNYL and QSNYL groups were 3.64 ± 2.34 and 4.08 ± 2.45, respectively (t = −4.00; p < 0.05). At the 3-month follow-up, three participants (4.05%) still had hyperpigmentation, and one (1.35%) had hypopigmentation. In this study, we adopted a randomized, blinded, and self-controlled method to objectively evaluate the efficacy and safety of PSNYL treatment for ephelides. Similarly, in our previous study, we compared the picosecond and Q-switched alexandrite lasers for treating ephelides and found no significant difference in the lesion clearance rate (0.769 vs. 0.756; p > 0.05).4 Compared with previous studies, this study has a larger sample size and is a two-center study. Melanosomes can more effectively absorb energy from a 532 nm laser, destroying the melanosomes. We used a PSNYL pulse width of 240–400 ps and QSNYL pulse width of 5–20 ns, both of which are significantly lower than the heat relaxation time (50–250 ns) of melanosomes and can effectively destroy the melanin particles in the epidermis. In this study, although there was a statistical difference of the lesion clearance rate between QSNYL treatment groups and PSNYL treatment groups, the two groups showed similar visual efficacy. However, shortening the pulse width has a positive effect; for example, for the treatment of nevus of Ota, a shorter pulse width can improve the efficacy of a single treatment significantly, reducing the number of treatments.5 All authors have read and approved the final manuscript. Y.Y., Z.X., L.G., Y.G., R.Y., and T.L. designed and performed the research study. Q.W., M.Z., R.Z., Y.A., Y.X., and W.W. contributed lesion counts. Y.Y. and Z.X. analyzed the data. Y.Y. and T.L. wrote the paper. CAMS Innovation Fund for Medical Sciences(CIFMS-2021-I2M-1-001). None to declare. This study was reviewed and approved by the Ethics Committee of Hospital for Skin Diseases, Chinese Academy of Medical Sciences Dermatology (No. 2019-LC-015), and that of The Seventh Medical Center of Chinese PLA General Hospital (No. LZEC-2019-QX-008). Clinicaltrials.gov listing: ChiCTR1900028336.