The title should be lacrimal obstruction. Lacrimal duct obstruction is a blockage of the passage of tears into the nasal cavity, and its clinical manifestation is mainly involuntary tearing. If the lacrimal duct obstruction is left untreated for a long time, or if the treatment is incomplete, local infections may occur, such as acute or chronic dacryocystitis, cellulitis, etc. Common causes of lacrimal obstruction include congenital anomalies and developmental factors (e.g. congenital HASNER flap obstruction, congenital atresia of the lacrimal duct, congenital absence of the tear dots, deviated nasal septum, etc.), inflammatory conditions (e.g. trachoma, acute and chronic conjunctivitis, chalazion infection, acute and chronic dacryocystitis, mydriasis, hypertrophic rhinitis, etc.), trauma (e.g. tear duct rupture, mechanical injury to the lacrimal duct and its vicinity, chemical injury, burns fractures of the nasal and maxillary bones involving the lacrimal duct), foreign body obstruction, lacrimal sac tumors, tumors of nasal origin, excessive and improper lacrimal duct irrigation and access, and surgically induced medical injury. The site of lacrimal duct obstruction can be determined by lacrimal duct irrigation test and x-ray lacrimal oil iodography. In conclusion, the causes of lacrimal duct obstruction are complex and should be examined by ophthalmology to remove the cause, control the local inflammation, and choose different treatment options according to the cause of lacrimal duct obstruction, such as lacrimal duct exploration and placement, lacrimal duct laser shaping, nasal lacrimal sac anastomosis, etc., to restore or establish lacrimal drainage channels.