Background: Picosecond (PS) lasers have evolved over the years, and several new wavelengths have been adopted for more efficient and safe treatment of various skin conditions. We specifically studied the 670 nm wavelength for its high melanin-hemoglobin ratio, effectiveness, and safety in laser-unfriendly Asian skin.
Objective: This study evaluated the effectiveness, safety, and patient satisfaction following treatment of solar lentigines and ephelides with a combination of a novel 670 nm PS and 1,064 nm wavelength laser in a series of Asian patients.
Methods: This retrospective study evaluated 30 patients who underwent treatment for solar lentigines and ephelides. A PS laser of wavelength 670 nm and 660 PS pulse width was adopted at a spot size of 2.0–3.5 mm, fluence of 0.7–0.8 J/cm², and repetition of 2.0–3.3 Hz. Treatment intervals ranged from 3–5 weeks for a total of 3–6 sessions. Skin pigmentations in the patients were documented with a high-resolution camera and the results were assessed by physicians. In addition, patient satisfaction was evaluated.
Results: Thirty patients (27 females, 3 males), aged 21–66 years, with Fitzpatrick skin type III or IV were treated and evaluated. It was observed that 100% of the patients achieved at least good results (>50% improvement), 80% achieved good results (>75% improvement), and 40% achieved clinical clearance (>90% improvement). The average downtime with mild redness was 2–3 days and transient darkening of pigmentation (crème brulee reaction) was observed for 5–7 days. Higher-contrast lesions demonstrated better responses. The post-inflammatory hyper- and hypopigmentation rates were 3.3% and 6.67%, respectively.
Conclusion: PS laser is effective for the treatment of solar lentigines and ephelides. The 670 nm wavelength is beneficial in improving the efficacy and safety of the PS laser treatment, which is especially important in Asian skin that is prone to laser complications.

Keywords: Asian, freckles, hyperpigmentation, laser, pigment

1. Negishi K, Akita H, Matsunaga Y. Prospective study of removing solar lentigines in Asians using a novel dual-wavelength and dual-pulse width picosecond laser. Lasers Surg Med 2018;50:851-8.
   
2. Chung JH, Lee SH, Youn CS, Park BJ, Kim KH, Park KC, et al. Cutaneous photodamage in Koreans: influence of sex, sun exposure, smoking, and skin color. Arch Dermatol 2001;137:1043-51.
3. Li EPH, Min HJ, Belk RW. Skin lightening and beauty in four Asian cultures. Adv Consum Res 2008;35:444-9.
4. Arora P, Sarkar R, Garg VK, Arya L. Lasers for treatment of melasma and post-inflammatory hyperpigmentation. J Cutan Aesthet Surg 2012;5:93-103.
   
5. Ho SG, Chan NP, Yeung CK, Shek SY, Kono T, Chan HH. A retrospective analysis of the management of freckles and lentigines using four different pigment lasers on Asian skin. J Cosmet Laser Ther 2012;14:74-80.