Nasolacrimal canal

The nasolacrimal canal is a bony structure within the skull that houses the nasolacrimal duct, which drains tears from the lacrimal sac into the nasal cavity. This canal plays a crucial role in the lacrimal apparatus, facilitating tear drainage and preventing overflow onto the face.

Anatomy

The nasolacrimal canal is formed by contributions from the following bones:

• Maxilla: Forms the majority of the canal.
• Lacrimal bone: Contributes to the medial wall.
• Inferior nasal concha: Contributes to the lower portion.

The canal begins at the lacrimal sac in the medial orbital wall and extends downward to open into the inferior meatus of the nasal cavity.

Function

The primary function of the nasolacrimal canal is to:

• Transmit the nasolacrimal duct, which carries excess tears from the lacrimal sac into the nasal cavity.
• Facilitate tear drainage to maintain a moist ocular surface and prevent tear overflow.

Clinical Significance

Disorders of the nasolacrimal canal can lead to tear drainage issues, including:

• Nasolacrimal duct obstruction (NLDO):
• Commonly caused by congenital anomalies, inflammation, or trauma.
• Symptoms include epiphora (excessive tearing) and recurrent infections.

• Dacryocystitis:
• Inflammation or infection of the lacrimal sac, often secondary to nasolacrimal duct obstruction.

• Trauma:
• Fractures involving the nasolacrimal canal can disrupt tear drainage and lead to complications.

Diagnosis

Common diagnostic methods for evaluating nasolacrimal canal disorders include:

• Dacryocystography: Imaging of the lacrimal drainage system using contrast.
• CT scan: Provides detailed anatomical views of the nasolacrimal canal and surrounding structures.
• Probing and irrigation: Used to assess patency of the nasolacrimal duct.

Treatment

Management of nasolacrimal canal disorders varies based on the underlying cause:

• Conservative management:
• Warm compresses and massage for mild obstructions.
• Antibiotics for infections such as dacryocystitis.

• Surgical interventions:
• Dacryocystorhinostomy (DCR): Creates a new pathway for tear drainage bypassing the obstructed nasolacrimal canal.
• Probing and stenting: Used for congenital nasolacrimal duct obstruction in infants and children.

See Also

• Lacrimal apparatus
• Tear film
• Inferior nasal meatus

References

1. Duke-Elder, W.S. "System of Ophthalmology: Anatomy of the Eye." London: Henry Kimpton, 1958.
2. Moukheiber, O., et al. "Disorders of the Nasolacrimal Canal." Clinical Ophthalmology, 2020.