The duct that drains tear fluid may get blocked and cause irritation to the eye.
As result of impaired tear drainage the eye is constantly watering. The coat around the corner of the eye appears damp and caked, forming a wet track towards the nose. If the condition persists for a longer period of time, the eye itself may become irritated and inflamed, resulting in conjunctivitis, keratitis, and possibly corneal ulcers.
The tear duct may become blocked by a foreign body or other space-consuming process, i.e. an abscess or a tumor. Infection can cause the duct to swell and thus impede drainage.
The tear duct has to be washed while the animal is under sedation. Foreign bodies may be expelled by passing a small tube through the duct. Abscesses or tumors may have to be removed surgically.
If you have observed symptoms of a blocked tear duct in your dog, consult a veterinary clinic. If symptoms of acute infection, i.e., pus, or pus-like discharge, are present, the condition should be examined sooner.