Figure 4: The intraocular vessels that nurture the lens and vitreous body during development are reabsorbed in mammals leaving an almost inert vitreous body and a partially unprotected optic disc. Vessels carry with them astrocytes that modify metabolically nearby axons. OC: Optic cup; OS Optic stalk; EL Embryonary lens; CF Choroid fissure; HA Hyaloid artery.