Fig. 4. Late fifth week demonstration of ocular development showing lens vesicle, two-walled optic cup and optic stalk with choroidal fissure incorporating the ophthalmic vessels. (Fries PD, Katowitz JA: Congenital craniofacial anomalies of ophthalmic importance. Surv Ophthalmol 35:87, 1990, with permission from Elsevier Science.)