In adults, a blocked tear duct can be caused by an injury to the bones and tissues around the eye, previous surgery around the eye and medications, explains Mayo Clinic. Other causes include eye infections, age related changes and tumors.
The symptoms of a blocked tear duct include excessive tearing, inflammation, recurrent eye infections, painful swelling at the corner or around the eye, drainage of pus or mucus around the eye lids and blurry vision, explains Mayo Clinic. The cause of the blockage can be determined using a tear drainage test, irrigation or probing, and eye imaging tests.
During a tear drainage test a drop of fluorescein dye is placed in each eye and the disappearance time is measured, according to Mayo Clinic. Each blink causes a little bit of the dye to disappear because of tear drainage. Blockage is diagnosed when the dye is still present after 5 minutes of blinking. Irrigation or probing is a procedure during which the opening of the tear duct is irrigated with saline to determine how well it drains. During the procedure the doctor may also insert a probe into the opening of the duct to evaluate the cause of the problem.
Dacryocystography is an eye imaging test during which a contrast dye is introduced into the opening of the tear duct, describes Mayo Clinic. The contrast passes through the drainage system and is visualized with an X-ray or an MRI. The doctor is able to see the area of blockage by looking at the distribution of the contrast.