Fig. 8. Drawing of cross-section at approximately 5 weeks' gestation through optic cup and optic fissure. The lens vesicle is separated from the surface ectoderm. Mesenchyme (M) surrounds the developing lens vesicle and the hyaloid artery is seen with the optic fissure. See also Figure 9F. (Cook CS, Sulik KK, Wright KW: Embryology. In Wright KW [ed]: Pediatric Ophthalmology and Strabismus, pp 3–43. St Louis: Mosby, 1995.)