From the retina the optic nerve runs back to the optic chiasm, where the fibres from the inner (nasal) half of each retina cross. The optic tract carries them on to the lateral geniculate body of the thalamus, and from there the optic radiation fans out to the visual cortex of the occipital lobe. [1][2]
The atlas draws the optic nerve, chiasm and tract but not the optic radiation; lit: the parts it runs through, in order.
The 3D brain needs JavaScript. The steps below still say where the visual pathway runs, in order.
The brain starts seen from below and a little from the left, where the optic nerves, the chiasm and the optic tracts lie on its underside. Step through lights one step at a time, about 1.2 s each, front to back; tap a step below to light it alone. Drag to turn, pinch or scroll to zoom. Step through is off because your device asks for reduced motion; tap each step instead.
Each step lights the whole part: the occipital lobe is lit entire, though the primary visual cortex covers only the banks of the calcarine sulcus, at its back and on its inner face. The optic radiation has no shape in the atlas, so its step lights nothing new. [3][4][5]
The route, in 6 steps
The axons of the retina’s ganglion cells, between about 770,000 and 1.7 million from each eye, gather at the back of the eye as the optic nerve and run back through the optic canal into the skull. [6][1]Where is the optic nerve?
The two optic nerves meet at the optic chiasm, under the front of the hypothalamus. Here the fibres from the inner (nasal) half of each retina cross to the other side, while those from the outer (temporal) half stay on their own side. [7][1]Where is the optic chiasm?
The crossing is partial: the nasal half of each retina sees the outer part of the visual field, so after the chiasm each optic tract carries everything seen on the opposite side, from both eyes. The left hemisphere sees the right half of the visual field. The atlas draws the chiasm but not the fibres crossing inside it. [7][2]
Behind the chiasm each optic tract curves back around the cerebral peduncle of the midbrain. Most of its fibres end in the lateral geniculate body; smaller branches go to the pretectal area and the superior colliculus. [8][2]Where is the optic tract?
The fibres end in the lateral geniculate body (nucleus), a six-layered relay of the thalamus: layers 1, 4 and 6 take the opposite eye, layers 2, 3 and 5 the eye on the same side, and the two bottom (magnocellular) layers carry different signals from the four upper (parvocellular) ones. [9]Where is the lateral geniculate body?
The optic radiation (geniculocalcarine tract) fans out from the lateral geniculate body, round the side of the lateral ventricle, to the visual cortex; its lower fibres first loop forward into the temporal lobe (Meyer’s loop), carrying the upper part of the visual field. The atlas has no shape for it, so this step lights nothing new: the lateral geniculate body it leaves from stays lit. [4]
The radiation ends in the primary visual cortex (V1, Brodmann area 17, the striate cortex) on the upper and lower banks of the calcarine sulcus, at the back and on the inner face of the occipital lobe; the upper bank receives the lower half of the visual field, the lower bank the upper half. [5][4]Where is the occipital lobe?
Each half of the visual field is handled by the opposite hemisphere: the right visual cortex sees the left half of the field, from both eyes. [2][7]
The centre of gaze (the fovea) takes up a far larger share of the visual cortex than its small area of retina, at the back tip of the occipital lobe. [5]
From V1 vision runs on in two streams: a ventral (“what”) stream into the temporal lobe and a dorsal (“where”) stream into the parietal lobe. [5][2]
Not every optic-tract fibre serves conscious sight: those to the pretectal area drive the pupil’s light reflex, and those to the superior colliculus help steer the eyes. [8][2]
Vision does not end in the occipital lobe: its streams run on into the temporal and parietal lobes. Every part, lit together with its role: What part of the brain controls vision?
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); it has no shape for tracts, so a pathway is shown by the parts it runs through.