Where the left and right optic nerves (CN II) meet and partially cross/decussate. The optic chiasm is located in front of the hypothalamus and above the pituitary gland. The fibers from the nasal retinas cross and join with the uncrossed fibers from the temporal retinas to form the optic tracts, which wrap around the base of the hypothalamus to reach the lateral geniculate nuclei in the posterior thalamus. Also see Bitemporal hemianopsia.
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