the eyes appear early in the fourth week in the form of a pair of lateral grooves , the optic sulci , which evaginate from the forebrain neural groove to form the optic vesicles .
References :-
1- Larsen's Human Embryology textbook ( Sixth Edition ).
2- the anatomy of human embryo electron microscope textbook ( 1st Edition ) .
3-langman medical embryology textbook ( Fourteenth Edition ).