Lacrimal Drainage Anatomy

Overview

The lacrimal system has two functionally distinct halves: a secretory side that makes the tear film, and a drainage side that clears it away. Basal tear production, the steady baseline wetting of the ocular surface, comes mostly from the accessory lacrimal glands of Krause and Wolfring, embedded in the conjunctiva. The main lacrimal gland, sitting in the superolateral orbit, works differently: it is primarily a reflex secretor, recruited by irritation, emotion, or foreign-body sensation rather than running continuously at rest. Everything either gland produces drains through one narrow, single-file path: puncta, canaliculi, lacrimal sac, nasolacrimal duct, nose. A block anywhere along that path, congenital or acquired, produces epiphora, covered on this site's epiphora page.

The Lacrimal Gland

The main lacrimal gland is divided into two lobes, orbital and palpebral, by the lateral horn of the levator aponeurosis, which splits through the gland as it passes laterally. This has a direct surgical consequence. Essentially all of the gland's excretory ducts, including those draining the orbital lobe, pass through the palpebral lobe on their way to the conjunctival fornix. A biopsy taken from the orbital lobe avoids cutting these ducts; one taken from the palpebral lobe risks transecting them and permanently reducing reflex tear secretion. That is why the orbital lobe, not the more accessible palpebral lobe, is the preferred biopsy site.

Secretomotor innervation to the lacrimal gland is parasympathetic, carried by fibers that synapse in the pterygopalatine ganglion before reaching the gland. This is the efferent limb of the reflex arc described below. The accessory glands of Krause and Wolfring, by contrast, make up only a small fraction of total lacrimal glandular mass, roughly a tenth, despite carrying the ongoing basal wetting of the ocular surface between reflex episodes.

Lacrimal gland development is not complete at birth. Newborns typically do not produce reflex tears when crying until roughly three weeks of age. A dry-eyed crying newborn at that age is a normal finding, not a sign of lacrimal gland disease.

The Lacrimation Reflex Arc

Reflex tearing runs through a defined neural arc. Corneal or conjunctival surface stimulation is sensed by the ophthalmic division of the trigeminal nerve (CN V), the afferent limb. That signal drives parasympathetic output through the facial nerve (CN VII), relayed via the pterygopalatine ganglion, to the lacrimal gland as the efferent limb. This is the same pathway responsible for reflex hypersecretion when the ocular surface is irritated, whether by a foreign body or by the surface inflammation of dry eye itself. It is why watery eyes are a common complaint in dry eye disease rather than a contradiction of it.

The Drainage Route: Punctum to Nose

Tears enter the drainage system through the puncta, one superior and one inferior, small openings on the medial eyelid margins. Immediately past each punctum the canaliculus widens briefly into a small dilation called the ampulla, then narrows again and runs first vertically, then medially, toward the lacrimal sac. In most people the superior and inferior canaliculi merge before reaching the sac, forming a single common canaliculus; a minority retain separate openings. That variant matters when interpreting a lacrimal syringing test: reflux confined to the injected canaliculus localizes a block proximal to that junction.

From the common canaliculus, tears enter the lacrimal sac, which sits in the lacrimal fossa at the medial orbital wall, then drain inferiorly through the nasolacrimal duct. The duct empties into the nose at the inferior meatus, beneath the inferior turbinate. At that terminal opening lies the valve of Hasner, a mucosal fold that is frequently not yet fully patent at birth. Its persistent membranous occlusion is the anatomical basis for congenital nasolacrimal duct obstruction, covered in depth on the epiphora page linked above.

Drainage is not purely passive. Blinking contracts orbicularis oculi fibers that surround the lacrimal sac, generating a pumping action that actively draws tears through the canaliculi into the sac, the so-called lacrimal pump. This matters clinically: the pump can fail even when the anatomical passage is completely open, producing watering despite a normal syringing test, again detailed on the epiphora page.

Canthal Anatomy

The medial canthus, the corner of the eye nearest the nose, is where the entire lacrimal drainage apparatus is concentrated: both puncta, the canaliculi, and the lacrimal sac all sit at or just deep to this landmark. That concentration explains two things. Medial eyelid lacerations require careful evaluation for canalicular injury, since trauma here can sever the drainage system even when the visible skin wound looks minor. And swelling, tenderness, or a mass at the medial canthus, as opposed to elsewhere on the lid, is the classic localizing sign of lacrimal sac pathology such as dacryocystitis or a mucocele.

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