Cranial nerve ii

1. OPTIC NERVEOPTIC NERVE

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

3. Functional components:
2.Special somatic afferents
3.Afferents for optical reflexes
Peculiarities:
2.Prolongation of white mater
3.Covered by meninges
4.Pial sheath carrying blood vessels
project into substance
5.Devoid of neurilemmal sheath
6.Myelination by oligodendrocytes

4. Course:
2.Intra-orbital part
3.Canalicular part
4.Intra-cranial part
Lesion:
2.Total blindness ipsilateral eye
3.Loss of ipsilateral direct and
contralateral consensual pupillary
light reflex
4.Retention of ipsilateral consensual
and contralateral direct light reflex
5.Unaffected accommodation reflex

5. VISUAL PATHWAYVISUAL PATHWAY
PrinciplesPrinciples

6. Receptors:
2.Rods
3.Cones
Neurons:
2.First order: bipolar cells
3.Second order: ganglion cells
4.Third order: LGB
Visuo-striate area (17):
Both walls of calcarine
sulcus involving Cuneus and
lingual gyrus

8. VISUAL PATHWAYVISUAL PATHWAY
ComponentsComponents

9. VisualVisual
PathwayPathway

10. VisualVisual
PathwayPathway
Optic chiasma:
•Junction of the floor and
the anterior wall of the
third ventricle
•Rests on the diaphragma
sellae
•Wilbrand’s loop

11. VisualVisual
PathwayPathway
Optic tracts:
2.Medial root
Gudden’s commisure
3.Lateral root
a.LGB
b.Superior colliculus &
pre-tectal nucleus
c.Supra-chiasmatic
nucleus

12. VisualVisual
PathwayPathway
Lateral geniculate body:
•Part of meta-thalamus
•Connected to superior
colliculus via superior
brachium
•Cells arranged in six layers

13. VisualVisual
PathwayPathway
Optic radiation:
•From LGB to striate area
of visual cortex (17)
•Passes through the retro-
Lentiform part internal
capsule
•Meyer’s loop

14. Pupillary light reflex
Direct
Consensual

15. AccommodationAccommodation

16. Accommodation
reflex

17. VISUAL PATHWAYVISUAL PATHWAY
LesionsLesions

18. LesionsLesions

19. LesionsLesions

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