Congenital Nasolacrimal Duct Obstruction

Sasha Mansukhani
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Congenital Nasolacrimal Duct Obstruction - Introduction
The tears from the conjuctival sac drain into the nose via the lacrimal drainage system. It consists of the inferior and superior puncta, the inferior and superior canaliculi, the common canaliculus, the lacrimal sac and the nasolacrimal duct (NLD), which drains via the inferior meatus into the nose.
While obstruction at any level in the drainage apparatus, can lead to ‘epiphora’ or excessive watering of the eye, the site of obstruction in infants is most commonly at the Valve of Hasner, which is located at nasal opening of the nasolacrimal duct(1). Symptomatic congenital nasolacrimal duct obstruction (CNLDO) occurs in 5 -6% of normal newborns(2).







Embryology (3)
The lacrimal drainage system begins to develop when the embryo is at the 7mm stage. The region between the lateral nasal and maxillary processes, has a groove called the naso-optic fissure. Thickening occurs at the base of this groove and a solid rod of cells separate to move deep to the surface at 43 days of age. This solid cord begins to canalize at 4 months of age, first in the region of the lacrimal sac, then the canaliculi and lastly the nasolacrimal duct. The membrane of the puncta is canalized by the 7th month of age, whereas the lower end of the nasolacrimal duct often has a persisting membrane even at birth. This imperforate membrane is the most common cause of neonatal epiphora. This also explains the higher incidence of congenital nasolacrimal duct obstruction (CNLDO) in premature infants(4). Abnormal embryogenesis, can lead to anomalies in other regions of the drainage apparatus too resulting in punctual atresia, absent canaliculus, duplicated canaliculus, lacrimal fistula and diverticulae.




Children with Down’s syndrome and craniofacial anomalies have a higher incidence of nasolacrimal duct obstruction. Some other syndromes associated with congenital nasolacrimal duct obstruction are Treacher Collins and Crouzons. Some craniofacial anomalies associated with nasolacrimal duct obstruction are cleft lip, cleft palate, bifid uvula and hemifacialmicrosomia(8).

The obstructed nasolacrimal duct (NLD), doesn’t allow the proper drainage of the tears and the mucous secretions, thus the excess tears spill out of the eye resulting in epiphora.

Rarely in approximately 0.1% of babies with nasolacrimal duct obstruction,a dacryocystocoele is formed(5). A dacryocystocoele is a distended lacrimal sac and is usually present perinatally(6). It is formed when the amniotic fluid or secretions enter, accumulate and distend the sac. This distension caused a kinking and functional obstruction of the common canaliculus not allowing the contents to escape. Thus valve like mechanism leads to tense distension of the sac. It is also called an amniontocoele(amniotic fluid) or mucocoele (mucous), indicating at the origin of the distending fluid, however ‘dacryocystocoele’ is an inclusive term that describes the location of accumulation, as origin of the fluid is not clinically distinguishable(7).

Neonatal dacryocystocoeles are almost always associated with nasolacrimal duct cysts(7). These are intranasal cysts formed due to increased hydrostatic pressure in the lacrimal drainage system, which causes outpouching of the imperforate membrane at the lower end of the NLD.


References
Congenital Nasolacrimal Duct Obstruction Congenital Nasolacrimal Duct Obstruction
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