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Opening of nasolacrimal duct

The opening of the nasolacrimal duct, also called the nasolacrimal orifice, is the distal exit of the nasolacrimal duct into the inferior meatus of the nasal cavity. It serves as the final passageway for tears draining from the lacrimal sac into the nasal cavity, playing a crucial role in tear drainage and ocular surface protection. Accurate knowledge of its anatomy and imaging characteristics is essential for radiologists, ophthalmologists, and ENT specialists, particularly in evaluating congenital anomalies, obstruction, or post-surgical outcomes.

Synonyms

  • Nasolacrimal orifice

  • Lacrimal duct opening

  • Distal nasolacrimal duct

  • Inferior meatus lacrimal opening

Function

  • Drains tears from the lacrimal sac into the nasal cavity

  • Maintains normal tear flow and ocular surface lubrication

  • Prevents tear overflow onto the cheek (epiphora)

  • Supports ocular health by facilitating tear drainage

MRI Appearance
T1-weighted images:

  • The nasolacrimal duct and its opening are small tubular structures, usually low signal intensity relative to surrounding soft tissue.

  • Air in the nasal cavity appears signal void (black), which sharply outlines the duct opening within the inferior meatus.

  • Surrounding mucosa and soft tissue structures show intermediate signal intensity, providing contrast to the lumen.

T2-weighted images:

  • Fluid within the nasolacrimal duct and sac appears hyperintense, making it distinguishable from surrounding soft tissue.

  • Air in the inferior meatus remains a signal void, helping define the opening.

  • Useful for detecting ductal obstruction, inflammation, or cystic dilatation.

STIR (Short Tau Inversion Recovery):

  • Suppresses fat signal in adjacent nasal and facial tissues, highlighting ductal pathology.

  • Normal duct remains low to intermediate signal, while inflammation, edema, or obstruction appears hyperintense.

CT Appearance

  • The nasolacrimal duct opening is visualized as a small air-filled or soft tissue-density structure in the inferior meatus of the nasal cavity.

  • Surrounding bony canal (nasolacrimal canal) is well visualized, allowing assessment for stenosis, fractures, or congenital anomalies.

  • Soft tissue density within the normally air-filled inferior meatus indicates obstruction, inflammation, or post-surgical changes.

  • CT is particularly useful for preoperative planning, trauma evaluation, or assessment of chronic dacryocystitis.

MRI images

Opening of nasolacrimal duct axial mri image -img-00000-00000