Congenital nasolacrimal duct obstruction is due to the unbroken Hasner valve at the lower end of the nasolacrimal duct in children at birth, and is a common disorder in pediatric ophthalmology clinics. The main clinical manifestations of congenital nasolacrimal duct obstruction or stenosis are prolonged tearing and inflammation, and it is the most important cause of chronic tearing in infancy. MacEwen et al. looked at 4,792 Scottish infants in order to study the prevalence and natural course of congenital nasolacrimal duct obstruction, and they found that close to 20% of infants had abnormalities of the lacrimal system in the first year of life. The disease is usually treated conservatively up to 3 months of age because it is somewhat self-healing. The method is to squeeze out the secretion from the lacrimal sac area first, then antibiotic eye drops, and then massage the lacrimal sac area after 5 minutes, 3 to 4 times a day. The method of massage is to squeeze the lacrimal sac from top to bottom of the lacrimal sac area below the nasal bone of the medial canthus with the fingertips of the index finger. Children with secretions from the extruded lacrimal sac area should undergo secretion culture and drug sensitivity testing to understand the causative organisms and to help select effective antibiotics. The self-healing rate of nasolacrimal duct obstruction decreases significantly after 3 months of age, so tear duct irrigation and tear duct probing can be performed early at 3 to 6 months. Tear duct probing can be performed if flushing is not successful. Early probing can shorten the duration of symptoms, reduce the economic and psychological burden of conservative treatment, and reduce the possibility of secondary infection. More importantly, in children older than 6 months, due to infection, the nasolacrimal duct scar proliferation is obvious, and the resistance to probing is greater, so not only the success rate of tear duct probing is reduced, but also the need for multiple probing. Therefore, parents should not delay the diagnosis and treatment, so as not to miss the best time for tear duct probing.