The developmental process pertaining to the initial formation of the optic vesicle from the lateral wall of the forebrain. This process begins with the specific processes that contribute to the appearance of the vesicle and ends when the vesicle has evaginated. The optic vesicle is the evagination of neurectoderm that precedes formation of the optic cup. [ GOC:ascb_2009 GOC:tb GOC:dph ]