The optic nerve begins at the optic disc and pierces the eyeball before entering the brain. It has several functional components and peculiarities, such as being covered by meninges and lacking a neurilemmal sheath. The optic nerve projects into the brain in three parts - intra-orbital, canalicular, and intra-cranial. Lesions can cause blindness, loss of pupillary reflexes, or retention of certain reflexes depending on the location. The visual pathway involves receptors in the eyes, bipolar and ganglion neurons, the lateral geniculate body, optic radiation, and visual cortex. Lesions in different parts of the visual pathway can result in scotomas, hemianopias or

1. OPTIC NERVE

2. Begins at the optic disc Pierces tunic of eyeball 3mm nasal to posterior pole

5. VISUAL PATHWAY Principles

8. VISUAL PATHWAY Components

9. Visual Pathway

14. Pupillary light reflex Direct Consensual

15. Accommodation

16. Accommodation reflex

17. VISUAL PATHWAY Lesions

18. Lesions

19. Lesions

21. 1 = Central scotoma secondary to optic neuritis 2 = Total blindness of the right eye from a complete lesion of the right optic nerve 3 = Bitemporal hemianopia from a complete lesion of the optic chiasm 4 = Right nasal hemianopia from a perichiasmal lesion 5 = Right homonymous hemianopia from a complete left optic tract lesion 6 = Right homonymous superior quadrantopia caused by partial involvement of the optic radiation in the left temporal lobe (Meyer's loop) 7 = Right homonymous inferior quadrantopia caused by partial involvement of the optic radiation in the left parietal lobe 8 = Right homonymous hemianopia from a complete lesion of the left optic radiation 9 = Right homonymous hemianopia (with macular sparing) from a posterior cerebral artery occlusion causing ischemia of the calcarine cortex of the occipital lobe