This is a blockage of the tear drainage system. The tear drainage system is composed of a nasolacrimal duct that collects tears at the tear lake and empties them into the nasal cavity near the front of the nose. The duct branches at the corner of the eye into two smaller collecting ducts—the upper and lower canaliculi – whose openings (called punctums) are located in the upper and lower eyelids.
A puppy can be born with a defective tear drainage system. In one condition, called imperforate inferior punctum, the duct system is normal except for a conjunctival membrane across the punctum of the lower eyelid. The problem occurs most often in Cocker Spaniels.
Other causes of nasolacrimal occlusion include entropion, in which the eyelid rolls inward and blocks the punctum; scarring of a punctum following a bout of purulent conjunctivitis; infection in a duct that causes cellular debris to plug the duct; and foreign bodies such as grass seeds that lodge in the ducts. These conditions usually cause tearing in only one eye.
The drainage system is first tested to see if it is open by staining the pool of tears with fluorescein dye. If the dye does not appear at the nostril, the system is blocked on that side. Nasolacrimal probes can be inserted into the ducts and various flushing techniques used to establish the point of obstruction. The flushing often removes the blockage and opens the duct.
Treatment: Nasolacrimal duct infection is treated with antibiotics, in some cases by instilling them directly into a duct. The dosage, type, and route of administration must be determined by your veterinarian.
A minor operation on a duct opening may be needed to clear a blockage. Follow-up treatment includes topical antibiotics and topical corticosteroids to reduce inflammation.