Optic tract root (CN II)

Radix tractus optici

NervousOrgansHead

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What it is
The start of each optic tract at the back corner of the optic chiasm, where fibres from both eyes regroup before sweeping round the cerebral peduncle toward the lateral geniculate body. Shown as a short stub on both sides; the nerve continues in the peripheral nervous system.
Function
Carries the opposite half of the visual field from both eyes.
Size
Stub about 1 cm; root 3.8 mm thick
Clinical note
A pituitary tumour pressing up on the chiasm from below classically causes bitemporal hemianopia.

Nearby nervous structures Arachnoid mater, Dura mater (cranial), Hypothalamus, Midbrain, Oculomotor nerve root (CN III), Olfactory tract root (CN I), Optic chiasm, Optic tract, Trigeminal nerve root (CN V), Trochlear nerve (CN IV)