The two optic nerves enter the cranial cavity and join in a structure known as the optic chiasma. Leading from the optic chiasma on either side of the brainstem is the optic tract. In the optic chiasma, the axons from the nasal (medial) halves of the retinas cross to the opposite sides.
Thus, the left optic tract contains all of the information from the left halves of the retinas (right visual field), and the right optic tract contains all of the information from the right halves of the retinas (left visual field).
The optic tracts carry this information to the LGB (lateral geniculate body) of the thalamus. From here, information is carried to the posterior medial portions (occipital lobes) of the cerebral cortex, where the information is perceived as conscious vision.
Note that the right visual field is perceived within the left hemisphere, and the left visual field is perceived within the right hemisphere.
The LGB also sends information into the midbrainstem. This information is used to activate various visual reflexes.