The optic vesicles project toward the sides of the head, and the peripheral part of each expands to form a hollow bulb, while the proximal part remains narrow and constitutes the optic stalk.

Closure of the choroidal fissure in the optic stalk occurs during the seventh week of development. The former optic stalk is then called the optic nerve. In short, the optic stalks are the structures that precede the optic nerves embryologically.

This article incorporates text in the public domain from page 1001 of the 20th edition of Gray's Anatomy (1918)