Tear duct irrigation is a commonly used examination in ophthalmology to determine lacrimal duct blockage and inflammation, which can be helpful in diagnosing lacrimal duct disease and in preoperative preparation. First, the eye is anesthetized locally, and a blunt lacrimal duct irrigation needle is inserted lightly into the upper or lower lacrimal duct, and saline is pushed into the lacrimal duct. If the pushed saline does not enter the oral cavity and pharynx, but returns the same way, it suggests that the lacrimal system may be blocked. Abnormal secretions found during flushing suggest a possible chronic lacrimal sac infection.