Fig. 7. Drawing shows formation of the lens vesicle and optic cup. Note that the optic fissure is present because the optic cup is not fused inferiorly. Mesenchyme (M) surrounds the invaginating lens vesicle. Note that the optic cup and optic stalk are made of neural ectoderm. (Cook CS, Sulik KK, Wright KW: Embryology. In Wright KW [ed]: Pediatric Ophthalmology and Strabismus, pp 3–43. St Louis: Mosby, 1995.)