The eyes begin to develop as a pair of diverticula (pouches) from the lateral aspects of the forebrain.

These diverticula make their appearance before the closure of the anterior end of the neural tube;[1][2] after the closure of the tube around the 4th week of development, they are known as the optic vesicles.

Previous studies of optic vesicles suggest that the surrounding extraocular tissues – the surface ectoderm and extraocular mesenchyme – are necessary for normal eye growth and differentiation.

[3] They 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, which goes on to form the optic nerve.

[4][5] This article incorporates text in the public domain from page 1001 of the 20th edition of Gray's Anatomy (1918)