By this partial decussation, the part of the visual field that is covered by both eyes is fused so that the processing of binocular depth perception by stereopsis is enabled (see Figure 2).

In mammals they also branch off to the lateral geniculate body of the thalamus, in turn giving them to the occipital cortex of the cerebrum.

[6] During development, the crossing of the optic nerves is guided primarily by cues such as netrin, slit, semaphorin and ephrin; and by morphogens such as sonic hedgehog (Shh) and Wnt.

[7] This navigation is mediated by the neuronal growth cone, a structure that responds to the cues by ligand-receptor signalling systems that activate downstream pathways inducing changes in the cytoskeleton.

[17] Since siamese cats, like albino tigers, also tend to cross their eyes (strabismus), it has been proposed that this behavior might compensate the abnormal amount of decussation.

[18][19] In cephalopods and insects the optic tracts do not cross the body midline, so each side of the brain processes the ipsilateral eye.

The crossing of nerve fibres, and the impact on vision that this had, was probably first identified by Persian physician "Esmail Jorjani", who appears to be Zayn al-Din Gorgani (1042–1137).