Congenital nasolacrimal duct obstruction is the most common cause of lacrimation and eye infections in infancy, the principle is the same as a household unit has a waterway and a sewer, the waterway comes from the “lacrimal gland”, located in the lacrimal fossa above the outer part of the eye, constantly secreting tears to moisten the eye, the eye’s sewer is called the “tear duct The lower waterway of the eye is called the “tear duct” and is composed of the tear duct, tear duct, tear sac, and nasolacrimal duct. Tears are diverted to the nasal cavity through this sewer. If there is a blockage in any part of this duct, it is called a lacrimal duct obstruction. A newborn baby cannot see if the tear duct is open because the tear ducts are not well developed and he cries without tears. Generally, after 3-4 weeks of life, the baby’s tear ducts gradually develop soundly, such as when the baby cries, tears are normal, if you observe that the baby has symptoms such as teary eyes when not crying, increased eye stool, etc., then parents should be alert, especially if one eye has tears and one eye does not have tears, then it is more indicative of abnormalities, then you should promptly take the baby to the hospital for examination. The best diagnosis is outpatient tear duct irrigation, if the irrigation is still ineffective 2~3 times, lacrimal duct exploration is needed. If congenital tear duct obstruction is left untreated for a long time, acute inflammation may occur and spread to the surrounding area; prolonged dilation of the tear sac will cause the tear sac wall to lose its elasticity, and later, even if the tear duct is open, tear overflow symptoms will still exist, and permanent scarring tear duct occlusion may be formed due to continued tear duct inflammation. In addition, the tear sac pus continuously drains into the conjunctival sac, which can lead to inflammation of the conjunctiva and cornea, causing corneal ulcers and even developing into endophthalmitis, posing a serious potential threat to the eye.