Valve of Hasner (Plica Lacrimalis)

Anatomy

The valve of Hasner is a mucosal fold (plica lacrimalis) located at the distal opening of the nasolacrimal duct into the inferior meatus of the nasal cavity, beneath the inferior turbinate. It is the terminal structure of the entire lacrimal drainage apparatus.

Tear drainage pathway (KJ Lee's Essential Otolaryngology):

Lacrimal puncta (upper & lower) → Canaliculi → Common canaliculus → Valve of Rosenmüller (prevents reflux into canaliculi) → Lacrimal sac → Nasolacrimal duct → Valve of Hasner → Inferior meatus

Location of the ostium (StatPearls): approximately 25-35 mm posterior to the external nares and 4-18 mm above the nasal floor. The opening type is variable - cadaveric studies show it is most commonly a vertical sulcus (70%), but can be oblique or fissure-like. The lacrimal fold itself is present in ~80% of specimens.

Function

The valve of Hasner acts as a one-way valve - it allows tears to drain into the nasal cavity but prevents nasal air and secretions from refluxing back up into the lacrimal system.

Embryology

The nasolacrimal system begins forming in week 5 of gestation from a cord of ectodermal tissue. Canalization proceeds throughout the system simultaneously from around week 8 onward. The valve of Hasner (the distal membrane) is the last part to canalize - it is imperforate in up to 70% of newborns at birth (Medscape). This usually opens spontaneously within the first month of life; if it persists, it causes congenital nasolacrimal duct obstruction (CNLDO).

Clinical Significance

1. Congenital Nasolacrimal Duct Obstruction (CNLDO)

The most important clinical association. An imperforate or strictured Hasner valve is the most common site of congenital lacrimal obstruction (KJ Lee's; Kanski's Clinical Ophthalmology).

Affects ~5% of infants symptomatically at birth; up to 20% show epiphora in the neonatal period
Presents with epiphora, eyelash matting, and mucopurulent discharge; mucus reflux on sac pressure
Spontaneous resolution occurs in ~90% by the first birthday - so probing should be delayed until age 1 (Kanski's)
If persistent: treatment is nasolacrimal duct probing (via upper canaliculus, observed endoscopically entering the inferior meatus through the Hasner valve), followed by intubation/stenting if needed

2. Nasolacrimal Duct Cyst (Dacryocystocele)

Failure of the Hasner valve to open leads to accumulation of secretions and expansion of the distal nasolacrimal duct, forming a cyst visible in the inferior meatus anterior to the duct opening (KJ Lee's).

3. Adults vs. Children in Obstruction

In young children, obstruction is predominantly at the imperforate Hasner valve (amenable to probing). In young adults, pathology tends to shift to the canaliculi (Cummings Otolaryngology).

4. Surgical Relevance

During dacryocystorhinostomy (DCR) and endoscopic nasal surgery, the Hasner valve and the duct ostium must be identified to avoid inadvertent injury, given the variability in their location
During probing, correct passage is confirmed endoscopically by visualizing the probe tip emerging through the Hasner valve into the inferior meatus (Scott-Brown's)
The proximity of the nasolacrimal system to the lateral nasal wall makes it at risk during inferior meatal antrostomy and turbinate surgery

Sources: KJ Lee's Essential Otolaryngology; Kanski's Clinical Ophthalmology 10th ed.; Scott-Brown's Otorhinolaryngology; Cummings Otolaryngology; StatPearls - Lacrimal Duct Anatomy; Medscape - Nasolacrimal System Anatomy

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