Structure and Development of the Optic Chiasm
- Optic nerves of left and right eye meet ventral to the brain
- Left optic nerve crosses over the right one without fusing
- Optic nerves merge in the optic chiasm in vertebrates with large overlap of visual fields
- Partial decussation allows for binocular depth perception
- Optic nerves become optic tracts, which insert on the optic tectum and lateral geniculate body
- Optic nerve crossing guided by cues such as netrin, slit, semaphorin, and ephrin
- Neuronal growth cone responds to cues and induces changes in cytoskeleton
- Retinal ganglion cell axons are blocked by Slit2 and Sema5A inhibition
- RGC axons change from retinotopic to flat sheet-like orientation near the chiasm
- Number of axons that do not cross the midline depends on degree of binocular vision

Function and Evolution of the Optic Chiasm in Different Animals
- Mammals possess optic chiasm, but its evolution is unknown
- Theories proposed for the function of the optic chiasm
- Siamese cats with certain genotypes of albino gene have disrupted wiring
- Optic tracts in cephalopods and insects do not cross the body midline
- Each side of the brain processes the ipsilateral eye in cephalopods and insects

History and Origins of the Optic Chiasm
- Persian physician Esmail Jorjani first identified the crossing of nerve fibers and its impact on vision
- Optic chiasm likely evolved as a consequence of a twist in the early embryo
- Siamese cats with disrupted wiring may compensate with strabismus
- Function of optic chiasm in vertebrates still not fully understood

Studies and Findings Related to the Optic Chiasm
- Semaphorin6D is presented in the optic chiasm
- Plexin-A1 and Nr-CAM are involved in the presentation
- The presentation promotes retinal axon midline crossing
- An ancestral axial twist explains the presence of the optic chiasm in vertebrates
- The axial twist hypothesis predicts opposite asymmetries in different body parts
- Albino cats exhibit abnormal retinotopic organization in the dorsal lateral geniculate nucleus
- The abnormal organization is linked to the absence of tyrosinase
- White tigers have genetic abnormalities in their visual pathways
- The abnormalities affect the visual pathways in the brain
- The cranial nerves have a long history of naming and classification
- The naming of the cranial nerves has evolved over time

Additional Images and Visualizations of the Optic Chiasm
- Scheme showing central connections of optic nerves and tracts
- Brain seen from below with optic chiasm labeled
- Transformations of visual field toward visual map on primary visual cortex
- Brain and brainstem seen from below
- Cerebrum, inferior view, deep dissection