optic nerve
describe the nerve fiber orientation
A. maculopillary B superior temporal C inferior temporal D superior nasal E inferior nasal F horizontal ralphe
what is present in the neural rim?
ILM and Nerve fiber layer
What are the three regions of the intraocular portion of the optic nerve?
Laminar = inside the lamina cribosa (collagen type I of the sclera) prelaminar = the nerve head proper, astrocytes arroung the axon bundles, make of ganglion axons, postlaminar = first millimeter of the optic nerve behind the eye, lower astrocytes, more oligodendrocytes(myalin sheeth)
what is the photo receptor concentration at the optic disk?
NONE! is the phyiological blind spot, two eyes + brain fils in the blind spots
what happens at the optic disk?
axons of the retina all converge here and exit the eye, central artery and vein enter and exit at the optic disc
What is papilledema?
caused by tumor, fraction of skil, change in intracranial pressure, causes a change in IOP
Describe the intermediary tissue of kuhnt
composed of astrocytes joined by TJ's, dividing line between the retina and the nerve fiber layer turning in to the optic nerve, create barrier function
what marks where the disk starts?
ending of the retina
describe the intraorbital optic nerve
extends to the apex of the orbit, surrounded by the rectus muscle and intraconal fat, sheath of the ON is continuous with SR and MR, can get optic neuritis - inflammation of the optic verde sheath, get pain because sensory nerves are in the sheath
How are the nerve fibers organized?
fascicles,, anterior to lamina cribosa are surrounded with astrocytes, posterior to lamina cribosa, nerve fibers become meylinated, additions Ct sheath is added
What are the regions of the optic nerve and were do they go?
fibers exit the optic nerve and go to LGN, takes a winding paht so that it dosen't get pulled with eye movements regions = intraocular: at the globe intraorbital: between glove and apex of orbit, with in the muscle cone intracanalicular: in the bone of optic foramen intracranial: between exiting the optic formen to the LGN
describe the border tissue of jocoby
found nasally, continuation of astrocytes covering with TJ, protects from high perimiablility of the CC. glial covering continues the length of the optic nerve
describe the marginal border tissue of elschnig
found temporally, between the astrocytes of the ON, and stroma of the choroid, is sometime covered by RPE
Where is the intracranal optic nerve
from the optic foramen to the chiasm
Where is the intracanalicular optic nerve?
in the optic foramen, created by sphenoid, small space that can cause damage
describe the internal limiting membrane of the optic nerve
inner most voering of the disc, with the highest density of astrocytes, continous with retinal ILM, continous though the cup
What is in each optic tract?
ipsilateral temporal fibers, contralateral nasal fibers
what is the meniscus of Kuhnt ?
is the optic cup, highest density of astrocytes
what causes the color change of optic disk due to?
layers of the retina are reduced to sclera and retinal vasculature, nerve fiber layer
What is the scleral crescent?
located outside the disc margin temporally, is a protrusion of the sclera between the optic nerve and ending of the choroid. fills in space becasue the optic nerve comes in medially, not visible in some people because covered by RPE in darker complexion people
What is the foramen that the optic nerve passes though and what creates it?
optic foramen or canal, formed by the lesser wing of shenoid
What are the layers of the optic nerve sheath?
outer = dura mater:external layer fuses with outer layers of sclera, arachnoid mater, pira mater = DCT with high vasculature subarachnoid space = continous with brain
what do macular fibers do?
temportal fibers merge with superior and inferior temporal fibers, nasal fibers cross in the superior-posterior aspect of the chiasm before exiting the contralateral optic tract
what is the physiologic optic cup?
the depression in the centre of the optic disc, colour usually lighter than the disc, depth caries, C/D ratio remains fairly stable
