21 - lesions of visual pathway and their presentations

Site of lesion	presentation	Common causes
Optic nerve	Ipsilateral blindness, absent ipsilateral direct light reflex, absent contralateral consensual light reflex	Optic atrophy, acute optic neuritis and traumatic avulsion of optic nerve
Sagittal (central) lesions of optic chiasma	Bitemporal hemianopia	Supra-sellar aneurysms, pituitary tumors,craniopharyngioma, glioma of the third ventricle
Lateral chiasmal lesions	Binasal hemianopia	Distension of the third ventricle and atheroma of the posterior communicating arteries
Optic tract	Homonymous hemianopia , wernick’s hemianopic papillary response	Syphilitic meningitis, tuberculosis and tumors of the optic thalamus , aneurysms of superior cerebellar or posterior cerebral arteries
Lateral geniculate body	Homonymous hemianopia with sparing of papillary reflexes	Syphilitic meningitis, tuberculosis and tumors of the optic thalamus
Optic radiation – total fibres involved	Homonymous hemianopia ( sometimes sparing the macula )	Vascular occlusion , primary and secondary tumors and trauma
Optic radiation – lower fibres only involved	Homonymous upper quadrantinopia ( pie in the sky )	Temporal lobe lesions
Optic radiation – upper fibres only involved	Homonymous lower quadrantinopia ( pie on the floor )	Anterior parietal lesions
Visual cortex	Homonymous hemianopia ( usually sparing the macula )	Vascular occlusion , primary and secondary tumors and trauma