Optic chiasma facts for kids

Visual pathway with optic chiasm (X shape outlined, red. Brain seen from underneath.

Scheme showing central connections of the optic nerves and optic tracts.

The optic chiasma, or 'optic chiasm', is the part of the brain where the optic nerves (CN II) partially cross. The optic chiasm is located at the bottom of the brain immediately below the hypothalamus.

Pathways

The images on the nasal (inner) sides of each retina cross over to the opposite side of the brain via the optic nerve at the optic chiasm. The temporal (outer) images, on the other hand, stay on the same side. This allows the images from either side of the visual field to go to the appropriate side of the brain, combining the sides together.

Beyond the optic chiasm, with crossed and uncrossed fibers, optic nerves become optic tracts.

The crossing over of optic nerve fibres at the optic chiasma allows the visual cortex to receive the same hemispheric visual field from both eyes.

The optic chiasma is found in all vertebrates.

Images for kids

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  Figure 2 Transformations of the visual field toward the visual map on the primary visual cortex in vertebrates. U=up; D=down; L=left; R=right; F=fovea

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  Brain seen from below, with the optic chiasm seen in yellow in the centre.

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  Transformations of the visual field toward the visual map on the primary visual cortex.

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  Guidance of axon crossing and non-crossing during development.