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Cranial Nerves
 
 

CN II: Optic Nerve

 
 
 
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Overview

  • Role

  • Special sensory (sight).

Optic Nerve Palsy

  • Abnormalities

  • Loss of visual acuity
  • Visual field loss
  • Loss of light reflexes
  • Loss of accommodation
  • Causes of Optic Nerve Palsy

  • Intraorbital - trauma, ischaemia, aneurysm, tumour, optic neuritis, optic nerve hypoplasia
  • Optic chiasm - pituitary tumour, craniopharyngioma, pituitary apoplexy
  • Optic tract - ischaemia, trauma, tumour, MS

Special Sensory Pathway

Cortical Centre
Primary visual cortex (occipital lobe)
 
Upper Pathway
Optic radiations
(parietal / occipital lobes)
 
Nucleus
Lateral geniculate nucleus (thalamus)
 
Lower Pathway
Optic tract
Partial Decussation
Of nasal / temporal visual field
Optic chiasm
Foramen
Optic canal
 
Bipolar Cells
Retina
 
 
Light Receptors
Rods / cones of retina

Overview

The optic nerve is encased in meninges, making it the only cranial nerve that is part of the central nervous system. As a result peripheral neuropathies such as Guillain-barré do not affect the optic nerve.
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