Visual Pathway Defect

Visual Pathway Defect 


Lesion in visual pathway → visual field defect depends on site.




Optic nerve → Monocular blindness.


Optic chiasma (central) → Bitemporal hemianopia.


Optic chiasma (lateral) → Ipsilateral nasal hemianopia.


Optic tract → Homonymous hemianopia (same side in both eyes).


Temporal lobe (Meyer’s loop) → Superior quadrantanopia (“pie in the sky”).


Parietal lobe fibers → Inferior quadrantanopia (“pie on the floor”).


Occipital lobe → Homonymous hemianopia ± macular sparing.


Common causes → Tumor, stroke, trauma, demyelination.


Causes of Visual Pathway Defects


Tumors: 

  • Pituitary adenoma (chiasmal), craniopharyngioma

Vascular: 

  • Stroke in posterior cerebral artery territory

Trauma:

  • Head injury affecting optic nerve or tract

Demyelinating disease: 

  •   Optic neuritis in multiple sclerosis

Congenital anomalies: Rare


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