Optimal Fluence and Duration of Low-Level Laser Therapy for Efficient Wound Healing in Mice

Background: Low-level laser (light) therapy is a promising technology that stimulates healing, relieves pain and inflammation, and restores function in injured body parts. However, few studies have compared the effects of lightemitting diodes of different fluence levels or different treatment durations. Objective: Here, we investigated the effects of various fluence levels and treatment durations on wound closure in mice. Methods: Full-thickness wounds were created on the dorsal skin using an 8-mm diameter punch, and the wounds were irradiated at 1, 4, or 40 J/cm2 for 5 consecutive days starting on day 1. To determine the optimal irradiation duration, wounds were irradiated at the most potent fluence of previous study for 5, 10, or 15 days. Photographic documentation, skin biopsies, and wound measurements were performed to compare the effects of different treatment parameters. Results: The most effective fluence level was 40 J/cm2 at day 5, as determined by monitoring wound closure. There were no statistically significant differences in wound healing with different durations. Conclusion: We have shown that repeated exposure to low levels of light significantly stimulates wound healing in mice and demonstrated more efficient wound closure with certain fluences of 830 nm irradiation. (Ann Dermatol 33(4) 318∼323, 2021)