Tear duct flushing examination is a routine examination method in ophthalmology, mainly used for the examination and diagnosis of lacrimal tract diseases. The method is usually to inject saline from the tear duct and determine whether there is lacrimal duct obstruction and the site of obstruction according to the flow direction of the rinsing fluid, which is usually seen in the following cases: first, there is no resistance to rinsing and the fluid enters the nasal cavity smoothly, indicating that the lacrimal duct is open. Secondly, the rinse fluid returns completely from the original way of injection, for the lacrimal duct obstruction. Thirdly, if the irrigation fluid is injected from the lower lacrimal duct and returned from the upper lacrimal duct, it is an obstruction of the common lacrimal duct, lacrimal sac or nasolacrimal duct. Fourth, there is resistance to flushing, part of the return from the tear dots, part of the flow into the nasal cavity, for nasolacrimal duct stenosis. Fifth, lacrimal duct irrigation fluid reflux from the upper tear dots, accompanied by a large amount of mucopurulent secretions, for nasolacrimal duct obstruction combined with chronic dacryocystitis.