Physiology
Optic nerve tract formed from temporal retina (medial view) and nasal retina (lateral view) from each eye
At optic chiasm, nasal tracts cross, so L temporal and R nasal to left hemisphere, R temporal and L nasal to right
So right side of vision controlled by L hemi and vice versa
Tract goes to lateral geniculate body then splits into superior and inferior radiations (lower and upper vision) then visual cortex)

Optic chiasm
Vascular: large internal carotid artery aneurysm
Neoplastic: craniopharyngoma, meningioma, pituitary tumour