Therapeutic efficacy of ultraviolet combined with riboflavin for the rabbit bacterial keratitis

Objective To study the effects of ultraviolet light combined with riboflavin treatment (corneal collagen-crosslinking, CXL) on infectious control and stromal reconstruction of bacterial keratitis. Methods Experimental Study. A Staphylococcus aureus rabbit keratitis model was established by injecting Staphylococcus aureus broth into the shallow stromal layer of the right eye cornea of New Zealand white rabbits. Forty-four rabbits that successfully established the model were randomly divided into four groups: corneal collagen cross-linking (CXL) group, antibiotic group, CXL+ antibiotic group and untreated group, with 11 rabbits in each group. Before the treatment and at 3, 7, 14 and 28 days after treatment, slit lamp corneal examination, AS-OCT and in vivo confocal microscopy (IVCM) were performed. Clinical efficacy of different treatments were evaluated at different time points. Parameters including conjunctival hyperemia, corneal ulcer, infiltration, edema, and neovascular. Histopathological examinations of corneal lesions were performed in order to detect the infiltration, inflammatory cells and repair in corneal tissue. Normal data were compared with paired t-test and non-normal data were compared with paired rank sum test before and after treatment. Kruskal-Wallis rank sum test was used to compare 4 groups of data and the generalized estimation equation is used to compare the repeated measurement data at each time point and the comparison between the groups of the treatment groups. Results After treatment, different time points and specimens for pathological observation, we obtained the following results:Conjunctival hyperemia: in CXL and CXL+ antibiotic groups after treatment for 3 days from treatment before 3 (2, -4) and 3 (2, -3),The reduction was 2 (1, -3) and 2 (1, -2), the difference was statistically significant (Z=-3.91, -5.50; P<0.008); 14 days, the antibiotic group changed from 3 (3, -4) to 2 (1, -2) after treatment, the difference was statistically significant (Z=-5.11, P<0.008); the untreated group had no statistical significance before and after treatment. After 14 days of treatment, the area of corneal ulcer (0.08±0.11) cm2, (0.07±0.05) cm2 in CXL group and CXL+ antibiotic group was significantly lower than that before treatment (0.40±0.18) cm2, (0.49±0.24) cm2. The difference was statistically significant. Significance (Z=-3.29, -3.64; P<0.008); after 14 days of treatment, after 14 days of treatment, neovascularization in the CXL and CXL+ antibiotic groups began to resolve, 1 (1, -2) and 1 (0, -2) at 7 days of treatment. decreased to 1 (1, -1) and 0 (0, -1), the difference was statistically significant (Z=4.57, 3.80; P<0.012 5); The degree of corneal edema was significantly reduced in the CXL group and the CXL+ antibiotic group at 14 days after treatment, which was reduced from (650±154) μm and (785±255) μm before the treatment to (432±95) μm and (455±109) μm, the difference was statistically significant (t=4.50, 4.92; P=0.00); The density of corneal stromal cells was also reduced from (446±257)/mm2, (321±145)/mm2 to (107±66)/mm2, (114±94)/mm2, the difference was statistically significant (t=4.15, 4.76; P<0.05). Histopathological observation under light microscope showed that most of the corneal ulcers healed in the CXL group and the CXL+ antibiotic group at 7 days of treatment. The epithelial cells were clearly visible and misaligned, and a small amount of neutrophils in the stromal layer. The upper epithelial layer was treated for 14 days. The cells are arranged neatly, the structure is clear, and the inflammatory cells are significantly reduced. Conclusion Ultraviolet light combined with riboflavin corneal collagen cross-linking has a certain therapeutic effect on rabbit bacterial keratitis infection control and ulcer repair, and can be used as an auxiliary treatment for antibiotics. (Chin J Ophthalmol, 2018, 54:902-910) Key words: Keratitis; Staphylococcal infections; Ultraviolet therapy; Riboflavin