Summary The Optic Nerve (CN II)

The Optic Nerve (CN II)


 This nerve has a special sensory function, carrying only special somatic
afferent fibres for sight
 It’s cell bodies are located in the ganglionic layer of the retina
 Axons of these ganglionic cells form bundles and leave the optic bulb as the
optic nerve




 Each optic nerve contains around 1 million myelinated axons
 Part of the meninges (pia mater) adheres to the optic nerve and is separated
from the arachnoid by the subarachnoid space
 The dura forms an outer sheath and fuses with the sclera of the eyeball
 The nerve travels posteromedially to exit the orbit via the optic canal
 From here it enters the middle cranial fossa where the optic fibres partially
cross at the optic chiasm
 This enables humans to have
binocular vision
 The optic chiasm is found
directly inferior to the
hypothalamus but superior to
the pituitary gland, so
compression by an enlarging
pituitary can cause bitemporal
hemianopia