As they carry neural messages to the visual centers in the brain, the optic nerves from each eye first come together in the optic chiasm; as they continue, one half of the fibers from each retina remain on the side of the body from which they originated.
The optic chiasm is a X shaped structure, part of the brain where the optic nerves partially cross
One-half of the nerve fibers from each eye continue on the same side of the brain, and the remaining nerve fibrts cross over at the chiasm to join fibers from the opposite eye on the other side of the brain.