the pit deepens to form the optic vesicle.

A small indentation in the central part of the optic placode. [157-169, Mueller_F_and_ObRahilly_R, The_first_appearance_of_the_neural_tube_and_optic_primordium_in_the_human_embryo_at_stage_10._Anatomy_and_Embryology_(1985)_172][VHOG]

uberon

optic evagination

(...) an essentially similar sequence of events occurs during the embryonic development of the vertebrate eye. The eye initially develops as a single median evagination of the diencephalon that soon bifurcates to form the paired optic vesicles (reference 1); The first morphological sign of eye development in vertebrates is the bilateral evagination of diencephalon in the early neurula. In mammals, this is marked by the appearance of the optic pit, whereas in fish and amphibians a bulging of the optic primordia is observed. Continued evagination of the optic primordia leads to the formation of the optic vesicles (reference 2).[well established][VHOG]

UBERON:0006270