When a tear duct is blocked, tears can't drain in the usual way, causing the eye to be watery and irritated. The condition is caused by a partial or complete blockage in the tear drainage system. A blocked tear duct is common in newborns. The condition usually gets better without any treatment during the first year of life. In adults, a blocked tear duct may be due to an injury, an infection or, rarely, a tumor. A blocked tear duct can almost always be treated. Treatment depends on the cause of the blockage and the age of the affected person.