Optic Nerve & Optic Chiasm: the 2^nd cranial nerves responsible for transmitting visual information from the retina to the occipital cortex of the brain. The optic nerves exit the orbit and pass through the optic canals (in the skull base) and into the intracranial space. A portion of each optic nerve crosses the midline above the pituitary gland to form the optic chiasm. Pressure on an optic nerve from a tumor causes monocular visual loss (in one eye only). Pressure from a tumor on the optic chiasm causes loss of peripheral vision in both eyes (also known as a bitemporal hemianopsia).