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The optic chiasm is found in all vertebrates, although in cyclostomes (lampreys and hagfishes), it is located within the brain. [2] [3] This article is about the optic chiasm of vertebrates, which is the best known nerve chiasm, but not every chiasm denotes a crossing of the body midline (e.g., in some invertebrates, see Chiasm (anatomy)).
The optic tract is a continuation of the optic nerve that relays information from the optic chiasm to the ipsilateral lateral geniculate nucleus (LGN), pretectal nuclei, and superior colliculus. [14] The optic tract represents the first stage in the visual pathway in which visual information is transferred in a homonymous nature. [15]
The decussation of the optic radiation in the cortex is an example of a type IV crossing. This type is usually not called chiasm. Such a looping occurs, for example, in the optic tract between the optic chiasm and the optic tectum. [6] Another example is the optic radiation which rotates the retinal map on the visual cortex by 180° (see Figure 3).
Bitemporal hemianopsia is the medical description of a type of partial blindness where vision is missing in the outer half of both the right and left visual field. It is usually associated with lesions of the optic chiasm, the area where the optic nerves from the right and left eyes cross near the pituitary gland.
[5] [6] Examples are provided as below: Optic nerve damage on the left (e.g. transection of left optic nerve, CN II, somewhere between retina and optic chiasma, therefore damaging the left afferent limb, leaving the rest of the pupillary light reflex neural pathway on both sides intact) will have the following clinical findings:
See for examples decussation of pyramids and sensory decussation. In neuroanatomy , the term chiasma is reserved for crossing of- or within nerves such as in the optic chiasm . In botanical leaf taxology , the word decussate describes an opposite pattern of leaves which has successive pairs at right angles to each other (i.e. rotated 90 degrees ...
Here is an example of an input image and how edge detection would modify it. Once the image is spatially encoded by the centre–surround structures, the signal is sent out along the optic nerve (via the axons of the ganglion cells) through the optic chiasm to the LGN (lateral geniculate nucleus). The exact function of the LGN is unknown at ...
Clinically, no optic field deficits have been observed in a small series of optic nerve sections at the optic nerve-chiasm junction. [3] Several important structures are located adjacent to the optic chiasm. The supraclinoid branches of the internal carotid artery flank the chiasm. The cavernous sinuses are lateral and inferior to the chiasm.