Optic tract

The optic tract is the posterior continuation of the optic chiasm, beginning at its posterolateral angle. Each tract passes posterolaterally around the diencephalon and upper part of the cerebral peduncle to reach the lateral geniculate body of the thalamus.

Each optic tract contains uncrossed fibres from the temporal half of the ipsilateral retina and crossed fibres from the nasal half of the contralateral retina. Consequently, the right optic tract carries information from the left visual hemifield, and the left optic tract from the right visual hemifield.

Destination sites of the optic tract fibres

Most optic tract fibres terminate in the lateral geniculate body, from which visual information is transmitted through the optic radiation to the visual cortex. Smaller groups of fibres pass to the pretectal region for the pupillary light reflex and to the superior colliculus for reflex orientation of the eyes and head toward visual stimuli.

Clinical correlate

A lesion of one optic tract therefore produces a contralateral homonymous hemianopia.