Abstract:  Objective To observe the pathological changes of the nasolacrimal duct at different time points after intubation and the biofilm on the surface of the stent. Design Experimental study. Participants  Eight New Zealand rabbits; the stents of 5 patients diagnosed with nasolacrimal duct obstruction and underwent intubation, who had no signs of infection in the postoperative period. Methods  A rabbit model of nasolacrimal duct obstruction was made, and intubation was performed after successful modeling. The rabbits were executed at 1, 4, 8, and 12 weeks after the operation (two rabbits per week), and the stent was dissected, and tissue sections were taken for observation. In all 5 patients, the duct was removed 12 weeks after surgery. Bacterial culture was performed on the removed stent. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fluorescence microscopy were employed to observe and analyze the stents. Main Outcome Measures  Inflammation and fibroproliferation of rabbit nasolacrimal and biofilm. Results HE staining indicated that at 1 week and 4 weeks after intubation, inflammatory cell infiltration and a small amount of epithelial cell shedding were observed in rabbits' mucosal epithelium and lamina propria of the nasolacrimal duct. At 8 weeks and 12 weeks after the operation, the shedding of mucosal epithelium was found to be increased compared with that before. Masson staining indicated that the collagen staining score was approximately 0.314 at 12 weeks after intubation, significantly higher than that at 1 week (0.023) and 4 weeks (0.076) after the operation. Inflammatory cell infiltration was the primary manifestation of rabbit nasolacrimal duct stent implantation at 1 week and 4 weeks postoperatively, and a small amount of epithelial cell detachment was seen. Fibroproliferation was significantly worse at 12 weeks postoperatively than before. Bacterial cultures of all 5 samples revealed positive aerobic bacteria, and 1 sample also showed positive anaerobic bacteria. Bacterial biofilms were observed in all samples, and SEM analysis indicated that these biofilms primarily consisted of cocci and rod-shaped bacteria with three-dimensional extracellular matrices and water channels. TEM suggests the presence of bacteria with intact structures in biofilms that are surrounded by a rich extracellular matrix. Fluorescence microscopy also revealed numerous bacteria on the surface. Conclusions Inflammation and fibrous proliferation of the nasolacrimal tissue after intubation may increase the rate of re-obstruction. In addition, biofilm colonization of the stent surface is common but does not necessarily lead to postoperative infection and recanalization failure.   

Key words: Intubation, Nasolacrimal duct obstruction, Biofilm