Keeping the eyes moist and healthy requires tears. Tears are produced in the lacrimal gland, located under the upper eyelid. Tears drain from the eye into the nose through the nasolacrimal duct, or tear duct. A blockage of this drainage duct can cause wet eyes or excessive tearing. A blocked tear duct can also cause mucus buildup in the eye or ongoing infections in the lacrimal sac where tears collect. Infections are noticeable as a swelling of the inner corner of the lower eyelid.

Nasolacrimal duct obstructions can happen with no obvious cause. Sometimes previous sinus or nose surgery, or facial trauma with broken facial bones, can obstruct the tear duct.

Lacrimal drainage surgery is called dacryocystorhinostomy (DCR) and can be performed in different ways. One type of operation is an external DCR where an incision is made on the side of the nose, where eyeglasses might rest. A small amount of bone is removed to permit a new connection between the lacrimal sac and the inside of the nose. Small plastic tubes are inserted at the time of surgery to keep the newly created opening from scarring shut during the healing process. The tubing is removed a few months after surgery.

Another type of operation uses a special instrument called an endoscope. The endoscope is a small tube with a fiberoptic light that facilitates the creation of a new opening into the nose. Various types of laser have also been used to perform the DCR operation.

In extreme cases where the tear duct cannot be reopened or repaired, an artificial tear duct can be implanted. The artificial tear duct is called a Jones tube and is implanted behind the inner corner of the eyelid to drain tears into the nose.