A common cause of epiphora in infants is due to a small membrane covering which structure?

Epiphora, or excessive tearing, in infants frequently arises due to a condition known as nasolacrimal duct obstruction. This obstruction often results from a membrane that fails to dissolve properly, leading to a blockage at the valve of Hasner, which is located at the opening of the nasolacrimal duct into the nasal cavity.

This small membrane typically persists due to developmental factors, preventing tears from draining from the eye properly into the nose, hence causing excessive tearing. When the nasolacrimal duct is obstructed, the tears collect in the conjunctival sac, leading to epiphora.

In contrast, the lacrimal gland is responsible for producing tears, while the canaliculus and puncta both play roles in the drainage of the tears into the nasolacrimal system. However, obstructions associated with those structures are less common as causes of epiphora compared to the blockage formed at the valve of Hasner in infants. This makes the valve of Hasner the most significant point of obstruction leading to epiphora in this age group.