2. Optic nerve head is formed in late embryonic
period as optic stalk encloses the hyloid artery.
(8th week)
Physiological cupping develops at 15th week.
Optic nerve develops from embryonic optic
stalk (4th week ) and connects optic vesicle to
fore brain.
As the stalks lengthens, nerve becomes thinner
and is progressively occupied by axons growing
from ganglion cell layer.
Myelination begins centrally, progresses in
centrifugal direction. Myelination is completed
shortly after birth.
3. Second cranial nerve.
Starts from optic disc, extends upto
chiasma.
Backward continuation of nerve fibre
layer of retina.
Also contains afferent fibres for l
i
g
ht
reflex.
4. An out growth of brain.
Not covered by neurilemma, so doesn’t
regenerate.
Surrounded by meninges.
Fiber diameter 2-10 microns. Sensory
nerve fiber diameter ~20 microns.
Both primary and secondary neurons i
n
retina.
Communications To
Sensory Tract of Brain
5. Total length 47-50mm
Divided into four parts:-
intra ocular part- 1mm
intra orbital part- 30mm
intra canalicular part- 6-9mm
intra cranial part- 10mm
6. Passes through sclera , choroid a
n
d
appears as optic disc.
1.5 mm vertical diameter.
Itself divided into:
Surface Nerve Fiber Layer
Prelaminar layer
Lamina cribosa
Retrolaminar region
7.
8. Extends from back of the eyeball to the
optic foramina.
Tortuous course to give room for o
c
u
l
a
r
movements.
Covered by dura, arachnoid and pia.
Pial sheath contains capillaries and s
e
n
d
septa to divide nerve into fasciculi.
Near optic foramen, optic nerve is
closely surrounded by annulus of zinn.
9. The long and short cilliary nerve a
n
d
arteries surround the nerve.
b/w optic nerve and lateral rectus
muscle are situated cilliary ganglion,
divisions of occulomotor, sympathetic
and abducent nerve.
The ophthalmic artery, sup ophth v
ei
n
and nasocilliary nerve cross the optic
nerve superiorly from lat to med side.
10.
11. Closely related to o
p
h
t
h
a
l
m
i
c
artery.
Leaves the sheath at the
orbital end of canal.
Sphenoid and post ethmoidal
sinuses lie medial to it and are
separated by thin bony lamina.
12. About 1cm in length.
Lies above cavernous sinus and
converges with the fellow nerve to
form optic chiasma over
diaphragma sellae.
Internal carotid runs first b
e
l
o
w
and then lateral to it.
The ant perforated substance,
med root of olfactory nerve and
ant cerebral artery lie above it.
13. In optic nerve head:
Same as in retina.
In distal region:
Temporal fibers situated in temporal half.
Upper and lower fibers separated by
pappilomacular bundle. Nasal fibers situated on
nasal side.
In proximal region:
macular fibers placed centrally.
Arrangement of Nerve
Fibres in Optic Nerve
14.
15. 1. Intraocular:
.SNFL- by anastomoses b/w
CRA, choriocapillaries and (if
present) cilioretinal arteries.
.Prelaminar and laminar
region- from short post
cilliary arteries.
.Retrolaminar region-pial
blood capillaries.
16.
17. 2. Intraorbital part :
supplied by two systems: axial and
periaxial.
Periaxial:
6 branches of ICA i.e. ophthalmic,
LPCA,SPCA, Lacrimal and central.
Axial:
intaneural branches of CRA.
21. Choroid smaller proportion.
Mainly by CRV and to alesser
extent by pial venous system.
Both systems drain into
ophthalmic venous system and
ultimaely into cavernous sinus.
22. Capillaries have non
fenestrated endothelial linings
with tight junction.
It is incomplete due to continuity
b/w extracellular space in choroid
and optic nerve.
There is no barrier present at t
h
e
level of choroid.
