valve of Hasner

(redirected from Hasner's valve)

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.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
The ostium is usually protected by a fold of mucous membrane called Hasner's valve. The easiest way to identify the opening of the nasolacrimal duct is to put light digital pressure on the lacrimal sac at the medial canthus while simultaneously observing the inferior meatus with the endoscope.
Care should be taken to avoid injury to the nasolacrimal duct and Hasner's valve. The trocar with sheath is passed through the ipsilateral canine fossa.