optic chiasma, optic chiasm, chiasma opticum(noun)

the crossing of the optic nerves from the two eyes at the base of the brain

optic chiasm(Noun)

The part of the brain where the optic nerves partially cross.

Optic Chiasm

The X-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes.