Clinical retrospective analysis of long-pulsed 1064-nm Nd:YAG laser in the treatment of onychomycosis and its effect on the ultrastructure of fungus pathogen

The objective of this study was to analyze retrospectively the clinical efficacy and fungal clearance of long-pulsed 1064-nm Nd:YAG laser for treating onychomycosis and explore the inhibitory effects of laser on the fungus pathogen-induced onychomycosis in vitro. We performed a systematic retrospective analysis of clinical patients (162 effected nails) of onychomycosis treatment applying laser with or without topical ketoconazole ointment and followed up 3 months after treatment. Trichophyton rubrum- and Trichophyton mentagrophytes-induced onychomycosis was irradiated with laser superimposed for different cumulative energy, respectively; then, the areas of fungus colonies and growth curve in different days were showed, and changes in ultrastructures were observed under SEM and TEM. The clinical effective rate and fungal clearance rate in the combined group were higher than those in the laser group; however, there was no significant difference between the two groups. In vitro, the areas of T. rubrum colonies were significantly reduced at days 1, 3, and 5 after irradiation with cumulative laser energy ≥ 6400 J/cm2. When irradiated with cumulative laser energy ≥ 25600 J/cm2, significant difference in the areas of T. mentagrophytes colonies was found at day 5. And ultrastructure of the two strains before and after laser irradiation was damaged at different degrees. This study confirmed that long-pulsed 1064-nm Nd:YAG laser is effective for treating onychomycosis, and the laser irradiation can inhibit the colony growth of T. rubrum and T. mentagrophytes and change their cellular ultrastructures. The mechanism of laser treatment of onychomycosis may be related to direct damage of fungus pathogen.