Visual pathway deficits

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 ¹:

• retina or optic nerve
  • anopia or central scotoma (ipsilateral)
• optic chiasm ²
  • 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 ³)
  • 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 ¹:

• 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
    • Bálint syndrome
  • occipitotemporal
    • achromatopsia
    • prosopagnosia
• left occipital lobe and angular gyrus
  • alexia without agraphia