The nasolacrimal duct is a tiny tube that joins a small orifice at the inside corner of the eye to another a few centimeters inside the nostril. Its function is to drain tears away from the eyes and into the nostril.

When the nasolacrimal duct is blocked for any reason, eye watering and tearing is the result. Blockage of the nasolacrimal duct can occur for a variety of reasons and almost always occurs when there is significant inflammation of the eye. Pus and debris block the duct.

Veterinary treatment involves flushing of the ducts, but identifying and treating any underlying disease or injury is very important.

Occasionally, there is a primary tear duct abnormality or injury. In these cases, the costs and benefits of surgery may be considered. The consequence of a non-functioning nasolacrimal duct is a watery eye.