What Are the Lacrimal Canaliculi?

Clara Kedrek

The lacrimal canaliculi, also known as the lacrimal ducts, are small anatomic structures that are part of the system that clears tears from the eyes. These small ducts connect two openings in the inner corners of the eyes to the nasolacrimal ducts, which empty tears into the nose. A number of problems can occur with these small tubes, including narrowing, blockage, and infection.

An infection of the lacrimal canaliculi can cause tears to overflow.
An infection of the lacrimal canaliculi can cause tears to overflow.

In order to understand the role of the lacrimal canaliculi, it helps to understand how tears are normally made and removed from the eyes. Production of the tears takes place in the lacrimal glands, which are located above the eyes.They secrete the tears into the upper outer corners of the eyes, and the blinking of the eyelids allows tears to be distributed equally over the surfaces of the eyes. Excess fluid collects in the inner corner of the eye, and eventually enters two little holes termed the puncta lacrimalia. The lacrimal canaliculi connect these two puncta to the lacrimal sac, which empties to the nasolacrimal duct that carries the tears to an opening in the inside of the nose.

Patients with poorly functioning valves of Rosenmuller may experience backflow of nasal secretions into the eye when they blow their noses.
Patients with poorly functioning valves of Rosenmuller may experience backflow of nasal secretions into the eye when they blow their noses.

Lacrimal canaliculi therefore serve as an important part of the outflow tract by which tears can leave the eyes. Each eye is drained by two canaliculi, although these canaliculi sometimes converge into one single tube before emptying into the lacrimal sac. The canaliculi are surrounded by elastic tissue, and can expand to two or three times their normal size when tear production is elevated. Reflux of fluid back into the eyes is typically prevented by the valves of Rosenm├╝ller.

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Canaliculitis often causes itchy eyes.
Canaliculitis often causes itchy eyes.

A number of problems with the lacrimal canaliculi can occur. Closure or narrowing of these ducts can result from a number of conditions. Some babies are born without their canaliculi having had a chance to fully open up, a condition known as congenital agenesis of the canalicular system. They often suffer from excessive tearing and redness of the eyes. Adults can also have blocked or narrowed canals, but this is typically acquired as a complication of infection with viral agents.

Small ducts in the corners of the eyes allow tears to empty into the nose.
Small ducts in the corners of the eyes allow tears to empty into the nose.

Certain pathogenic agents can selectively infect the lacrimal canaliculi, resulting in a condition called canalicultis. Affected patients experience itchiness, redness of the eye, and discharge from the inner corner of the eye. This can be caused by infection with Candida albicans, Actinomyces israelii, or http://www.wisegeek.com/preview.htm?id=188364 species. Without proper treatment this infection can cause a blockage of these ducts.

Another problem that people can have with their lacrimal canaliculi is poorly functioning valves of Rosenm├╝ller. These patients can have backflow of nasal secretions up into the eye. When they blow their noses, they might notice either air bubbles or a watery discharge in their eyes. Although this might be concerning to patients, it is typically a benign condition.

Someone with congenital agenesis may suffer from redness of the eyes.
Someone with congenital agenesis may suffer from redness of the eyes.

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