optic cup, a two-layered embryonic cavity that develops in early pregnancy. The optic cup is completed by the seventh week with the closing of the choroidal fissure. The cup initially develops from the infolding of the optic vesicle after the vesicle separates from the embryonic ectoderm. The cells of the optic cup differentiate to form the retina that first develops its layers of rods and cones in the central part of the cup, growing as the layer gradually spreads toward the cup margin. The outer layer of the cup persists as the pigmented layer of the retina; the inner layer develops the nervous elements and the supporting fibers of the retina. Compare optic stalk.
