Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

y excessive tearing. Excessive tearing may also be caused by eye irritation
due to extra eyelashes or facial hairs that rub on the surface of the eye.
Treatment: For treatment of epiphora, see Poodle Eye, page 190.
NASOLACRIMAL OCCLUSION
THE EYES • 189
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.
Lower
Caniculus
The Nasolacrimal Duct System
Upper
Caniculus
Nasolacrimal
Duct