Lacrimal Puncta - BDS 1st Year Anatomy

Overview of the Lacrimal Apparatus

The lacrimal apparatus consists of structures that produce and drain tears. The drainage pathway runs:

Lacrimal gland → Tear film on eye surface → Lacrimal lake → Lacrimal puncta → Lacrimal canaliculi → Lacrimal sac → Nasolacrimal duct → Inferior nasal meatus

Lacrimal apparatus - full schematic showing punctum, canaliculi, sac and nasolacrimal duct

Fig. 24.21 - Histology: A Text and Atlas

Lacrimal Puncta - Definition

The lacrimal puncta (singular: punctum) are the small openings of the lacrimal canaliculi through which tears enter from the lacrimal lake. They are the beginning of the lacrimal drainage pathway.

Position / Location (Important for exams)

There are two puncta - one on each eyelid (upper and lower lid)
Located at the medial angle (medial canthus) of each eye
Situated at the posterior edge of the lid margin, at the junction of:
- The lash-bearing lateral 5/6 of the lid margin (pars ciliaris)
- The medial non-ciliated 1/6 (pars lacrimalis)
Normally, the puncta face slightly posteriorly (toward the eyeball), which is why you need to evert the medial lid to inspect them properly
The punctum and the vertical portion of the canaliculus are part of the tarsal plate

Structure

Each punctum leads into a lacrimal canaliculus, which has two parts:

Part	Description
Ampulla (vertical part)	~2 mm long, runs vertically downward from the punctum before turning
Horizontal part	~8 mm long, runs medially toward the lacrimal sac

The superior and inferior canaliculi usually unite (in >90% of people) to form a common canaliculus
The common canaliculus opens into the lateral wall of the lacrimal sac
A small mucosal flap called the Valve of Rosenmüller (internal punctum) covers this junction and prevents reflux of tears back into the canaliculi

Lacrimal drainage system with measurements - Ampulla 2mm, Canaliculus 8mm, Sac 10mm, Duct 12mm

Fig. 3.1 - Kanski's Clinical Ophthalmology, 10th Ed.

How Tears Flow Through the Puncta (Physiology)

Tears are secreted by the lacrimal gland (upper lateral orbit) via ~12 ducts into the superior fornix of the conjunctiva
Blinking spreads tears across the cornea from lateral to medial
Tears accumulate in the lacrimal lake (medial angle of the eye)
From the lacrimal lake, tears enter the puncta by capillary action and suction
With each blink, the pretarsal orbicularis oculi muscle:
- Compresses the ampullae
- Shortens and compresses the horizontal canaliculi
- Closes and moves the puncta medially - preventing reflux
- Simultaneously, the lacrimal part of orbicularis oculi creates positive pressure that forces tears down the nasolacrimal duct
When the eyes open, the canaliculi and sac expand, creating a negative pressure that draws fresh tears from the puncta into the sac

Lacrimal sac - showing puncta and canaliculi

Fig. 8.88 - Gray's Anatomy for Students

Complete Drainage Pathway with Measurements

Structure	Length
Vertical canaliculus (Ampulla)	~2 mm
Horizontal canaliculus	~8 mm
Lacrimal sac	~10-12 mm
Nasolacrimal duct	~12-18 mm

The nasolacrimal duct opens into the inferior nasal meatus (below the inferior nasal concha), and its opening is partially covered by the Valve of Hasner (a mucosal fold).

Related Muscles

The lacrimal part of orbicularis oculi (Horner's muscle) surrounds the horizontal canaliculus. Its contraction during blinking is the key pump mechanism that drives tears through the puncta and down into the nasal cavity.

Clinical Relevance (Important for BDS viva)

Condition	Key Point
Punctal stenosis	Narrowing of the punctum causing watery eye (epiphora)
Punctal malposition (ectropion)	Punctum turns outward, cannot contact the lacrimal lake
Dacryocystitis	Inflammation of the lacrimal sac, often from obstruction of the nasolacrimal duct
Congenital nasolacrimal duct obstruction	Valve of Hasner fails to open at birth; most common cause of watery eye in neonates
Epiphora	Overflow of tears onto the cheek due to obstruction or malposition anywhere in the drainage system

Quick Exam Recall Points

Two puncta per eye - one upper, one lower
Located at the medial canthus, on the posterior edge of the lid margin
Each leads into a canaliculus with a 2 mm vertical part (ampulla) + 8 mm horizontal part
Upper and lower canaliculi join as a common canaliculus in >90% cases
Valve of Rosenmüller - prevents reflux at entry to lacrimal sac
Valve of Hasner - at opening of nasolacrimal duct into inferior meatus
Drain ultimately into the inferior nasal meatus
Blinking is the active pump - driven by orbicularis oculi (Horner's muscle)

Sources: Gray's Anatomy for Students; Kanski's Clinical Ophthalmology 10th Ed.; Histology: A Text and Atlas (Pawlina)

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