Nasolacrimal

Nasolacrimal refers to the tear drainage system that connects the eyes to the nasal cavity. The nasolacrimal apparatus includes the lacrimal gland, the tear drainage ducts, and the nasal portion via which tears exit the eye surface into the nose. Specifically, tears produced by the lacrimal gland wash across the ocular surface and drain through the puncta on the medial edges of the upper and lower eyelids, into the canaliculi, then to the lacrimal sac, and finally through the nasolacrimal duct to the inferior meatus of the nasal cavity. The distal end of the nasolacrimal duct is guarded by Hasner’s valve, which helps regulate drainage into the nasal cavity.

Function and physiology: The nasolacrimal system maintains tear film turnover, clears excess tears, and removes debris from the ocular surface. Blinking and eyelid movement create a pumping action that facilitates tear flow through the puncta and canaliculi. Proper drainage prevents excessive tearing (epiphora) and helps protect the eye from infection and irritation by maintaining a stable tear film environment.

Clinical relevance: Congenital nasolacrimal duct obstruction (NLDO) is common in infants and presents with excessive tearing and mucous discharge. Many cases resolve spontaneously by 6–12 months of age; persistent obstruction may be treated with lacrimal sac massage or probing and dilation. Acquired NLDO occurs in adults due to infection, chronic inflammation, trauma, or tumors and often requires procedures such as dacryocystorhinostomy (DCR) to restore drainage. Diagnostic imaging, including dacryocystography or lacrimal scintigraphy, may be used to evaluate obstruction or drainage patterns.

Development and variation: The nasolacrimal system develops from embryonic structures near the nose, and canalization progresses during fetal life. Anatomical variations and concurrent nasal pathology can influence tear drainage efficiency.