Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
the constricted proximal portion of the optic vesicle in the embryo; it contributes to the formation of the optic nerve.
1. A double layered cup-shaped structure attached to the forebrain of the embryo by means of a hollow stalk. It develops into the retina and inner layers of the ciliary body and iris. It is formed by the invagination of the outer wall of the optic vesicle. Subsequently, nerve cells develop in its invaginated layer and some of these send their axons back along the hollow stalk (optic stalk or lens stalk) to form the optic nerve. Syn. ocular cup; ophthalmic cup; secondary optic vesicle.