Samiksha Jaiswal (Editor)

Optic radiation

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Latin
  
radiatio optica

Dorlands /Elsevier
  
r_01/12686139

NeuroNames
  
ancil-529

FMA
  
61941

Optic radiation

TA
  
A14.1.08.673 A14.1.09.542 A14.1.09.547

The optic radiation (also known as the geniculocalcarine tract, the geniculostriate pathway, and posterior thalamic radiation) are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex. The optic radiation receives blood through deep branches of the middle cerebral artery and posterior cerebral artery.

Contents

They carry visual information through two divisions (called upper and lower division) to the visual cortex (also called striate cortex) along the calcarine fissure. There is one such tract on each side of the brain. If a lesion only exists in one optic radiation, the consequence is called quadrantanopia, which implies that only the respective superior or inferior quadrant of the visual field is affected.

Structure

The upper division:

  • Projects to the upper bank of the calcarine fissure, called the cuneus
  • Contains input from the superior retinal quadrants, which represents the inferior visual field quadrants
  • Transection causes contralateral lower quadrantanopia
  • Lesions that involve both cunei cause a lower altitudinal hemianopia (altitudinopia)

    • The lower division:

  • Loops from the lateral geniculate body anteriorly (Meyer's loop), then posteriorly, to terminate in the lower bank of the calcarine sulcus, called the lingual gyrus
  • Contains input from the inferior retinal quadrants, which represents the superior visual field quadrants
  • Transection causes contralateral upper quadrantanopia
  • Transection of both lingual gyri causes an upper altitudinal hemianopia

    • Parts

    A distinctive feature of the optic radiations is that they split into two parts on each side:

    Function

    The optic radiation contains tracts which transmit visual information from the retina of the eye to the visual cortex. Lesions of the optic radiations are usually unilateral and commonly vascular in origin. Field defects therefore develop abruptly, in contrast to the slow progression of defects associated with tumors.

    Examination

    Tracts contained within the optic radiation are examined as part of a cranial nerve examination.

    References

    Optic radiation Wikipedia
    (Text) CC BY-SA