Benign pigmented lesions can be divided into epidermal lesions such as freckles, lentigines, solar lentigines or cafe au lait macules and dermal lesions such as Nevus of Ota or Hori's nevus.~Q-switched 532 and 1064 nm lasers were reported to be safe and effective in the treatment of these benign pigmented lesions. By using selective photothermolysis theory, both q-switched 532 and 1064 nm lasers target on melanin causes photomechanical destruction of the melanin. However, the occurrence of post inflammatory hyperpigmentation (PIH) were reported especially in patients with darker skin type.~Recently, picosecond 532, 755, 1064 nm laser was reported to treat benign pigmented lesions effectively. With their ultra short pulse duration (picosecond domain), it is ideally believed to be pure photomechanical effects without thermal injury to surrounding tissue. As a result, the incident of PIH should be reduced.~The investigators then aimed to compared the efficacy and efficacy of different pulse duration between nanosecond and picosecond laser in the treatment of benign pigmented lesions.
The objective of this study is to evaluate the efficacy and safety of picosecond 532 and 1,064 nanometers laser in the treatment of benign pigmented lesions compared with q-switched 532 and 1,064 nanometers laser.