What is a common cause of epiphora in infants?

Epiphora, or excessive tearing, in infants is often caused by an obstruction in the nasolacrimal duct, which can occur where the duct opens at the valve of Hasner. In infants, the valve of Hasner, located at the distal end of the nasolacrimal duct, may not be fully patent at birth, resulting in tears not being able to drain properly. This leads to the accumulation of tears and, consequently, epiphora.

While the lacrimal gland, canaliculus, and puncta are all important components of the tear drainage system, they are not the primary causes of excessive tearing in this age group. The lacrimal gland produces tears, and the canaliculus and puncta are responsible for the initial drainage of tears into the nasolacrimal system. However, if there is a blockage at the valve of Hasner, tears cannot flow into the nasal cavity adequately, causing overflow and the symptom of epiphora in infants.