5. Optic Nerve
Lamina cribrosa provides structural support.
Lamia cribrosa: Type I,III,V,VI with intersposed
elastic fibers.
Ophthalmic artery short PCA (segmental)
Watershed area (PCA anastomoses are scant).
Circle of Zinn-Haller.
8. Intracanalicular Optic Nerve
Within the two bases of the LWS.
Medial wall of canal forms lateral wall of
sphenoid sinus (can be absent !).
Within canal : meninges, ophthalmic artery and
sympathetic plexus.
10 mm length.
Tight space !
Internal carotid artery.
9.
10. Intra-orbital Optic Nerve
Myelination (oligodendrocytes).
20-30 mm Long.
Axons: mylein and glial cell (metabolic support
at the nodes of Ranvier).
11. Optic nerve (Intracranial)
Leaves the cranial end of the optic canal (medially,
backwards, upwards).
4-15 m (depending on the position of chiasm).
Upward 45 degree-angle.
Anterior cerebral and anterior comunicating artery lie
superior.
12. Physiology of the Optic Nerve
Axoplasmic transport : clearance of expired
organelles, structural maintainance, and energy
requirements.
Interruption of axoplasmic transport : ischemia,
compression, inflammation.
Orthograde axonal transport : away from the cell
body LGN.
Retrograde axonal transport : toward cell body.
13. Physiology of the Optic Nerve
Orthograde fast and slow speeds.
Proteins, transmitters transported in smooth
surface vesicles at 400 mm/day (5 hours to
LGB).
Elements of cytoskeleton (microtubules,
neurofilaments) dependant on actin, kinesin and
dynein.
Mitochondria moving in both orthograde and
retrograde fashion.
16. Optic chisam
Floor of the third ventricle.
5-10 mm above the diphragma sella and the hypophysis
cerebri.
12mm wide, 8mm A-P , 4 mm thick.
Important relations: 3rd ventricle, hypothalmus, pituitary
stalk, sella, dorsum sellam anterior and posterior clinoid
processes, cavernous sinus.
Nasal fibers cross ; temporal fibers do not (53:47).
Wilband’s knee.
20. Chiasm
90% of chiasmal fibers have macular origin
(superior and posterior portions of chiasm).
Supraclinoid portions of carotid artery lie lateral
to chiasm.
22. Optic tracts
Travel around the cerebral peduncles at dorsal
midbrain.
Divides into lateral root LGN , and a smaller
medial root pretectal area (pupillary light
reflex).
23. Lateral Geniculate Bodies
Part of the thalamus.
Hilum, medial and lateral horn.
Six laminae (layers 1-6), crossed fibers1,4,6 ,
uncrossed fibers 2,3,5.
medial
lateral
24. LGN
Upper quadrant medial aspect of LGN,
Lower quadrant lateral aspect of LGN.
Macular fibers central wedge of LGN.
Layers 1,2: magnocellular. (motion)
Layers 3-6: Parvocellular. (color)
25. Optic radiations
Nerve fibers bundles with cell bodies in the
LGN.
Loop of Meyers (around temporal and inferior
horn of LV).
Inferior fascicle.
Superior fascicle.
26. Optic radiations
Inferior fascicle anterior pole of temporal
lobe lower calcarine cortex.
Superior fascicle parietal lobe upper
calacrine cortex.
27. Visual cortex
Upper bank and lower bank (Calcarine fissure).
LGN input into layer 4 (Stria of Gennari ).
Inferior visual filed (upper bank) , Superior
visual field (lower bank).
28. Visual cortex
-Maculr projections represented by
50%-60% of the area of the calcarine
cortex.
-Occipital tip is for foveal vision.
-Anterior striate cortex (8%-10%) is
monocularly innervated (temporal
crecsent of contralateral eye).
34. Problem 2
A 55 year old patient with sudden, pain less
vision loss in her left eye.
Visual acuity : OD-20/200 OS-20/25
Color vision : OD- Nil OS-8/8