Tags: Anatomical Structure.
The plica semilunaris is a small fold of bulbar conjunctiva on the medial canthus of the eye. It functions during movement of the eye to help maintain tear drainage via the lacrimal lake and to permit greater rotation of the globe for without the plica the conjunctiva would attach directly to the eyeball restricting movement. It is the vestigial remnant of the nictitating membrane (the third eyelid) which is drawn across the eye for protection.
