Nasal hemiretina
Retina · Temporal field of same eye
Ganglion cells of the nasal half of each retina, which see the temporal half of that eye's field, including the far-peripheral temporal crescent that only the nasal retina sees. Their axons decussate in the optic chiasm to join the contralateral optic tract, which is why chiasmal lesions are bitemporal.
Detail
- Field served
- Temporal hemifield of the same eye
- At the chiasm
- Crossed (about 53% of fibres)
- Destination
- Contralateral optic tract, LGN layers 1, 4 and 6
- Crossing order
- Inferior nasal fibres cross low and anteriorly; superior nasal fibres cross high and posteriorly
When it goes wrong
Loss of the crossing nasal fibres of both eyes at the chiasm
Bitemporal hemianopia: each eye loses its temporal field, so the patient keeps central acuity but loses stereopsis and bumps into objects on both sides
Practise this structure
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