Synergistic treatment for Nevus of Ota: Distinct and complementary functions of ablative fractional laser and Q-switched laser

A novel synergistic treatment protocol is proposed for Nevus of Ota (NO), which utilizes ablative fractional laser (AFL) to create micro-ablative zones (MAZs) prior to Q-switched laser, integrating the distinct functions and obtaining complementary synergistic improvement. A numerical model integrating multilayer Monte-Carlo light propagation and local thermal non-equilibrium equation was employed to calculate the photo-thermal treatment of Q-switched laser in the NO skin with different combinations of MAZ density and depth, which was determined by an AFL ablation model based on the ablation enthalpy theory. Simulations for diffuse and superficial NOs reveal that the therapeutic depth is maximized when MAZ depth is encapsulated within the thermal ablation front at a distance of twice the single-MAZ penetration-enhancing ablation length. Denser and shallower MAZ combinations usually yield larger therapeutic volumes, but my lead to severer side-effects. Balancing efficacy and safety, we recommend the implement of 10,600 nm AFL (300MAZ/cm2, 64 mJ) to create MAZs (300MAZ/cm2, 1000 μm depth) prior to Q-switched 1064 nm laser. For patients sensitive to side-effects, a combination of 200 MAZ/cm2 and 1500 μm depth (98 mJ), or other sparser and shallower combinations, may be considered.