visual pathway deficits

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Visual pathway or visual field deficits are defects in visual space determined by the location of a lesion in the neurological visual pathway from eye to brain cortex. Understanding of the visual system is paramount :

  • retina or optic nerve
    • anopia or central scotoma (ipsilateral)
  • optic chiasm 
    • anterior (at the junction with one of the optic nerves)
      • junctional scotoma (ipsilateral central scotoma with contralateral superotemporal/temporal field defect)
    • middle
      • bitemporal hemianopsia (central lesions involving crossing fibers; classic)
      • binasal hemianopsia (bilateral lesions involving noncrossing fibers; rare )
    • posterior (at the junction with one of the optic tracts)
      • scotomatous bitemporal hemianopsia
  • optic tract
    • homonymous hemianopsia
  • lateral geniculate nucleus
    • homonymous sectoranopia or hemianopsia
  • temporal lobe
    • homonymous upper quadrant defect ("pie in the sky" quadrantanopia)
  • parietal lobe
    • homonymous defect, denser inferiorly (inferior quadrantanopia)
  • occipital lobe 
    • complete
      • isolated homonymous defect (macular sparing)
    • lower bank
      • homonymous upper quadrantanopia with macular sparing
    • upper bank
      • homonymous lower quadrantanopia with macular sparing

Vison abnormalities other than visual field deficits can also help localize lesions :

  • retina, optic nerve, optic chiasm, or contralateral optic tract
    • relative afferent pupillary defect (Marcus-Gunn pupil)
  • bilateral lesions
    • occipital lobe
      • Anton syndrome (cortical blindness)
    • occipitoparietal
    • occipitotemporal
      • achromatopsia
      • prosopagnosia
  • left occipital lobe and angular gyrus
    • alexia without agraphia