valve of Hasner

valve of Hasner 

A fold of mucous membrane at the lower end of the nasolacrimal duct. If well developed, it generally prevents air from being blown back from the nose into the lacrimal sac. Syn. plica lacrimalis; valve of Bianchi. See lacrimal apparatus.
References in periodicals archive ?
45-47) A negative finding where no fluorescein is observed indicates an obstruction, which may be anywhere from the punctum to the valve of Hasner.
In congenital nasolacrimal duct obstruction block is at lower membranous part and valve of Hasner.
Duct is guarded by a membranous valve known as valve of Hasner at the opening in the inferior meatus, nature has created this valve to prevent nasal secretions entering into the eye which is a potential source of infection.