Transcription factor that is required for closure of the choroid fissure and together with Vax2 is required for optic nerve differentiation and to limit retinal development to the optic cup. Expressed in the anterior neural keel and later in the preoptic area and optic stalk. First detected in the anterior neural keel at 7 somites. By 12 somites, expression is more robust in the medial forebrain and forming eyes. By 16 somites, expression remains within the optic stalk and is predominantly restricted to tissue ventral to the optic stalk and ventral preoptic area. In addition to optic stalk and ventral preoptic area, weakly expressed in the ventral retina near the choroid fissure region by 24 hpf (hours post-fertilization). At 48 hpf, expression remains prominent in the ventral preoptic area but is much reduced in the choroid fissure and optic stalk. Belongs to the EMX homeobox family.