Objective To construct a carbon dioxide(CO2)laser-induced corneal injury model in mice and observe the process of corneal wound healing.Methods Twenty eyes of ten C57BL/6J mice were divided into 4 groups.The cen-tral corneas in each group were irradiated by CO2 laser with a wavelength of 10.6 μm,spot diameter of 2 mm and power of 0.94 W.The exposure doses were 3.0 J·cm-2,4.5 J·cm-2,7.5 J·cm-2 and 10.5 J·cm-2,with corresponding expo-sure durations of 0.10 s,0.15 s,0.25 s and 0.35 s.Corneal injury severity was assessed using a slit lamp microscope,opti-cal coherence tomography and histopathological evaluation at 1 day after the exposure to determine the proper exposure dose for constructing a corneal injury model.Subsequently,the corneal injury model was constructed and the same meth-ods were used to monitor wound healing before,and 0 hours to 6 months after the exposure.Results No obvious corne-al injury was observed at an exposure dose of 3.0 J·cm-2.At an exposure dose of 4.5 J·cm-2,an off-white injury area appeared on the central cornea with loss of epithelium and endothelium.At an exposure dose of 7.5 J·cm-2 or 10.5 J·cm-2,the injury area became porcelain white,the cornea was thickened,and the iris was seen adhering to the margin of the cornea.Therefore,4.5 J·cm-2 CO2 laser was selected to construct a corneal injury model.At this exposure dose,the cornea swelled and thickened rapidly after injury,reached the maximum thickness 1 day after the exposure,and then grad-ually recovered,returning to normal by 14 days after the exposure.In the early stage(0 hours to 3 days after the expo-sure),the cornea showed shedding of injured epithelium and endothelium,migration of new epithelium and endothelium,and infiltration and regression of inflammatory cells.At the late stage(7 days to 6 months after the exposure),the cornea gradually returned to a normal physiological state,but some of the injured cornea exhibited stromal hyperplasia.Conclu-sion A CO2 laser with an exposure dose of 4.5 J·cm-2 can be used to construct a corneal injury model in mice.The a-cute phase of corneal injury primarily occurs within 3 days after the exposure.The cornea tends to restore its original physi-ological structure,but the corneal transparency cannot return to a normal state.

Objective To explore the corneal wound healing mechanism after 3.74 μm infrared laser irradiation.Methods Twenty-seven C57BL/6J mice(six to eight weeks old)were randomly divided into a normal group(3 mice)and an experimental group(24 mice).Mice in the normal group were not subjected to any treatment.The corneas of mice in the experimental group were damaged by infrared laser at a wavelength of 3.74 μm.The spot diameter was 2 mm,the exposure duration 0.8 s,and the radiant exposure 23.2 J·cm-2.Pathological sectioning of corneas was performed at 3 h,6 h,12 h,1 d,3 d,7 d,14 d,and 21 d after laser irradiation in the experimental group,with 3 mice at each time point.It was the same for mice in the normal group.Immunohistochemical staining was conducted to examine neutrophil elastase,CD68,CD163 and thrombomodulin-positive cells and identify neovascularization.Results Neutrophil elastase,CD68,CD163,and thrombomodulin-positive cells were not detected in the corneal stroma of mice in the normal group.Neutrophil elastase-positive cells were detected in the damaged corneal periphery of mice in the experimental group at 3 h,migrated to the damaged area at 12 h,peaked at 1 d,and then decreased gradually with time,but still existed slightly at 21 d after laser irradiation.CD68-positive cells were detected in the damaged corneal periphery of mice in the experimental group at 12 h and in the damaged area at 1 d through 21 d after laser irradiation.CD163-positive cells were found in the damaged corneal periphery of mice in the experimental group at 7 d and in the damaged area at 14 d and 21 d after laser irradiation.Throm-bomodulin-positive cells were found in the damaged area of the corneal stroma at 14 d and 21 d after laser irradiation.Con-clusion During the wound healing process after 3.74 μm infrared laser-induced full-thickness corneal injury in mice,a large number of inflammatory cells migrate from the damaged corneal periphery or limbus to the damaged area.Neutrophils and M1 macrophages infiltrate in the early stage,while M2 macrophages are involved in the later stage,accompanied by neovascularization.