730-nm, 532-nm and 694-nm laser in the treatment of freckles and solar lentigines (A randomized clinical trial)

Objective: This study aims to assess the effectiveness and safety of the 730-nm picosecond laser, the 532-nm picosecond laser, and the Q-switched 694-nm nanosecond laser in treating freckles and solar lentigines. Methods: The randomized clinical trial included 42 participants who met the specific eligibility criteria for freckles and solar lentigines. On each participant’s face, three distinct skin areas affected by these conditions were identified and randomly assigned to receive treatment with the 730-nm picosecond laser, the 532-nm picosecond laser, or the Q-switched 694-nm nanosecond laser. Treatments were administered at one-month intervals, with follow-up assessments at 1, 3, and 6 months post-treatment. Evaluation criteria encompassed: (1) the Researchers’ Global Aesthetic Improvement Scale (GAIS) scores, (2) the Subjects’ Self-Rated Satisfaction (SSS) scores, (3) the Visual Analogue Scale (VAS) scores for pain severity, (4) the Lesion Clearance Rate, (5) numerical analysis of Individual Type Angle (ITA°), and (6) histological analysis. Adverse reactions, including skin edema, erythema, scab formation, pigmentation changes, were meticulously documented throughout the study. Results: All 42 subjects completed the treatment and follow-up phases. Significant improvements in skin clearance rates and individual type angle were observed following the three distinct laser treatments (P < 0.05). However, no significant difference were found in the global aesthetic improvement, participant satisfaction, or individual type angle scores across the three laser types (P < 0.05). Notably, there were substantial differences in pain severity scores as measured by the VAS among the three laser treatments (P < 0.05). Additionally, the duration of erythema, edema, and scab resolution varied significantly among the three laser treatments (P < 0.05). Histological analysis revealed minimal vacuolar degeneration in basal cells post 730-nm picosecond laser treatment, moderate vacuolar degeneration following the 532-nm picosecond laser, and extensive continuous vacuolar degeneration in basal cells after Q-switched 694-nm nanosecond laser treatment. Conclusion: The 730-nm picosecond laser, 532-nm picosecond laser, and Q-switched 694-nm nanosecond laser all demonstrate efficacy in treating freckles and solar lentigines. In terms of safety, the 730-nm picosecond laser stands out with less histological damage, suggesting it may be a preferable treatment option for pigmentary conditions in future clinical practice.