 Er:YAG ablative fractional laser-assisted photodynamic therapy AFL-PDT has shown significant benefit for the treatment of actinic keratosisAK. Er:YAG ablative fractional laser ablates the epidermis and dermis without significant thermal injury, creating microscopic ablation zones MAZ in the portion of the skin that the laser is applied to. The formed MAZ depends on the laser parameters such as laser depth, laser density and laser passes, which affect the treatment outcome. 