Tear drainage !

The tear drainage system is a set of tiny channels, a sac and a duct that carry tears from the inner corner of the eye into the nose.

Official name: Lacrimal canaliculus

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What it is

Tiny channels from the inner corner of the eyelids into a sac and a duct that opens into the nose.

What it does

Drain tears into the nose; a blocked duct causes a watery eye.

Key facts

Where: Puncta -> canaliculi -> lacrimal sac -> nasolacrimal duct -> inferior meatus
Function: Drains tears into the nose

Relations

Course: From the puncta on the medial lid margins, the canaliculi run medially behind the medial canthal tendon to the sac; the nasolacrimal duct then descends in a bony canal of the maxilla, slightly backward and outward, to the inferior meatus
Medial: Between the sac and the nasal cavity, at the front of the middle meatus, lie the lacrimal bone and the maxilla's frontal process, and sometimes anterior ethmoid cells
In front: Medial palpebral ligament across the upper part of the sac; skin, with the angular vein a little medially
Behind: Lacrimal part of orbicularis oculi (Horner muscle), attached to the posterior lacrimal crest; orbital septum
Lateral: Along the nasolacrimal duct, the maxillary sinus beside its bony canal

How to find it

The puncta sit on small raised papillae at the inner end of each lid margin, turned toward the eye, and show when the lid is drawn gently away. The sac lies in the bony groove at the inner corner of the eye, behind the medial canthal tendon, which stands out as a cord when the lids are pulled outward. The lower opening of the duct is seen under the inferior concha on nasal endoscopy.

Examination

Fluorescein dye disappearance test: dye placed in both lower fornices clears within a few minutes in a normal system; dye retained on one side suggests a block (useful in children)
Lacrimal irrigation through a punctum: fluid reaching the nose means the system is open; reflux from the same punctum points to a canalicular block, reflux from the opposite punctum to a block in the common canaliculus, sac or duct
Pressure over the sac that brings mucus or pus out of the puncta shows a blocked nasolacrimal duct with a chronically infected sac

On imaging

Dacryocystography (contrast injected into a canaliculus) outlines the level of a block, and dacryoscintigraphy shows how well tears drain. CT is used after naso-orbito-ethmoid fractures or when a tumour of the sac is suspected.

Common problems

Blocked tear duct: a constantly watery eye; common in babies and older adults.
Dacryocystitis: an infected, swollen tear sac by the nose.

How it is diagnosed

Flushing the duct with saline and dye tests.

Treatment

Massage in babies (most open by themselves).
Probing, or surgery to make a new path into the nose (dacryocystorhinostomy).

Clinical notes

Congenital nasolacrimal duct obstruction: watering and sticky discharge from the first weeks of life; most open on their own within the first year, and persistent cases are probed
Dacryocystitis: a red, tender swelling below the medial canthal tendon; a mass above the tendon is atypical and raises concern for a tumour of the sac
Dacryocystorhinostomy (DCR) bypasses a blocked duct by joining the sac to the nasal cavity through an opening in the lacrimal bone and frontal process of the maxilla, by an external or endoscopic route
A watery eye in an adult may come from too many tears (irritation, ectropion) or poor drainage; a punctum turned away from the eye is a common, simple cause in older people

Development

The duct forms from a solid cord of surface ectoderm buried along the nasolacrimal groove, between the maxillary and lateral nasal prominences; it hollows out from above downward and the lower end opens last, which explains congenital obstruction.

Test yourself

Think of the answer, then tap the question to see it.

What is the path of tear drainage from the eye to the nose?

Puncta, canaliculi, lacrimal sac, nasolacrimal duct, then the inferior meatus under the inferior nasal concha.

Where is the usual site of congenital nasolacrimal duct obstruction, and how does it usually evolve?

The membrane at the lower end of the duct (valve of Hasner); most open on their own within the first year.

Where does dacryocystitis swell, and what does a mass above the medial canthal tendon suggest?

Below the medial canthal tendon, red and tender; a mass above the tendon is atypical and raises concern for a tumour of the sac.

What does a dacryocystorhinostomy (DCR) do?

It bypasses a blocked nasolacrimal duct by joining the lacrimal sac to the nasal cavity through an opening in the lacrimal bone and maxilla.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): canaliculus lacrimalis TA2 6855
Official Spanish (DeCS): Vías lagrimales DeCS D009301
English (TA2): Lacrimal canaliculus
Also called: tear duct · ductus lacrimales · ductuli lacrimales

Sources: Terminologia Anatomica (TA2); DeCS; Anatomy, Head and Neck: Eye Nasolacrimal; Anatomy, Head and Neck: Eye Lacrimal Duct; Anatomy of the Human Body (20th ed.): The Accessory Organs of the Eye (Lea & Febiger (Gray's Anatomy, 1918), 1918) · adapted, Public domain.

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Representative model, for educational purposes only.

Tear drainage highlighted on the Durgical 3D model