A blocked tear duct is when the eye's drainage system for tears is either partially or completely obstructed. Tears cannot drain normally, causing a watery, irritated or chronically infected eye.
Most of your tears come from your lacrimal glands, which are located above each eye. The tears flow down the surface of your eye to lubricate and protect it, and then drain into tiny holes (puncta) in the corners of your upper and lower eyelids. The tears then travel through the small canals in the lids (canaliculi) to a sac where the lids are attached to the side of the nose (lacrimal sac), then down a duct (the nasolacrimal duct) before emptying into your nose, where they evaporate or are reabsorbed.
A baby can be born with a blocked tear duct (a congenital blocked tear duct). It is estimated nearly 20 percent of newborns have a blocked tear duct, but the condition usually resolves on its own within four to six months. In adults, the tear duct obstruction can result from an eye infection, swelling, injury or a tumor.