Histologic analysis of a 2,940 nm fractional device

Background and Objectives An evaluation of the histological effects of a 2,940 nm fractional erbium:YAG (Er:YAG) laser device with adjustable depth and coagulation settings in a human abdominoplasty model. The goal of this study was to use light and confocal microscopy to determine the dimensions of the microthermal zones (MTZs) created by this device in the epidermal and dermal layers. Study Design/Materials and Methods Three subjects were consented and treated after being randomly assigned to a laser depth of either 250 μm, 500 μm, or 1,000 μm. Four coagulation levels were tested in each subject. Two biopsies were taken immediately, 1 and 2 weeks post-treatment from each zone and viewed by light and confocal microscopy. Two blinded observers examined the sections for changes in collagen and measured depth and width of the MTZs. Coagulation was assessed and recorded as the depth and width of denaturation; measured as the depth and width of ablation plus surrounding thickness of thermal necrosis from dissipated heat. Results Light microscopy findings in all treated samples showed a perforated epidermis and dermis immediately after treatment. The depths of ablation produced did not accurately reflect the three different laser settings. Depths of denaturation also did not increase with increased coagulation level settings as expected. The width of ablation in the MTZs, a non-adjustable setting, was the most accurate and reproducible in all subjects. Confocal microscopy samples revealed the presence of collagen remodeling in the dermis, which increased significantly at 1 and 2 weeks post-treatment. Conclusions Treatment with the 2,940 nm Er:YAG device led to significant changes of the dermis at light microscopy levels. The adjustable laser depth and coagulation settings did not produce predictable depths of ablation or denaturation, possibly as a result of the variation of tissue hydration properties among individuals. Increased collagen remodeling was seen in the dermis in all subjects at 1 and 2 weeks post-treatment.