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Visual field defects

The main points for the exam are:
- left homonymous hemianopia means visual field defect to the left, i.e. Lesion of right optic tract - homonymous quadrantanopias: PITS (Parietal-Inferior, Temporal-Superior) - incongruous defects = optic tract lesion; congruous defects = optic radiation lesion or occipital cortex

A congruous defect simply means complete or symmetrical visual field loss and conversely an incongruous defect is incomplete or asymmetric. Please see the link for an excellent diagram.

Homonymous hemianopia

  • incongruous defects: lesion of optic tract
  • congruous defects: lesion of optic radiation or occipital cortex
  • macula sparing: lesion of occipital cortex

Homonymous quadrantanopias*

  • superior: lesion of the inferior optic radiations in the temporal lobe (Meyer's loop)
  • inferior: lesion of the superior optic radiations in the parietal lobe
  • mnemonic = PITS (Parietal-Inferior, Temporal-Superior)

Bitemporal hemianopia

  • lesion of optic chiasm
  • upper quadrant defect > lower quadrant defect = inferior chiasmal compression, commonly a pituitary tumour
  • lower quadrant defect > upper quadrant defect = superior chiasmal compression, commonly a craniopharyngioma

*this is very much the 'exam answer'. Actual studies suggest that the majority of quadrantanopias are caused by occipital lobe lesions. Please see the link for more details.