Ocular: Optic Nerve Flashcards
What cranial nerve is the optic nerve?
CN 2 (lol just incase we forget HAHAHA)
Where is the optic disc located relative to the macula
Nasal to the macula
Approx. how many retinal ganglion cell axons for the optic nerve are in each eye?
1.2 - 2.2 million
What retinal layer is formed by the axons of the retinal ganglion cells?
The retinal nerve fiber layer
What are the four divisions of the optic nerve? What is the total length?
- Intraocular
- Intraorbital
- Intracanalicular
- Intracranial
-4-5cm long
What are the dimensions of the optic disc?
1.9mm vertical and 1.5mm horizontal
In what direction is the optic cup displaced in relation to the disc?
Slightly temporal from the center of the disc
Does the optic cup have nerve fibers?
No
What does the neuroretinal rim contain? Where is it located?
-contains nerve fibers
-located between the margin of the optic disc and cup
What is the cup-to-disc ratio?
A comparison of the diameter of the cup to the overall diameter of the disc used to assess changes in the neurological rim thickness over time
What side of the cup do the central retinal blood vessels emerge?
The nasal side of the cup
What layers are in the “prelaminar” portion of the optic nerve?
The retinal part and the choroidal part
What layers are the in the “post laminar” part of the optic nerve?
The scleral part (lamina cribrosa)
What is the lamina cribrosa?
The region of the sclera where the optic nerve fibers pass through
What are the glial borders of the optic nerve?
-meniscus of kuhnt
-inner limiting membrane of elsching
-border tissue of elsching
-border tissue of Jacoby
-intermediary tissue of Kuhnt
-internal limiting membrane of retina
What is the meniscus of kuhnt?
Glial plaque (astrocytes) that line the optic cup
What is the internal limiting membrane of elsching?
Peripheral continuation of meniscus of kuhnt that lines the surface of the neuroretinal rim
What is the border tissue of elsching?
Collagen separating choroid from bundles of optic nerve fibers
What is the border tissue of jacoby?
Glial tissue between the border tissue if elsching and optic nerve fibers.
-merges with 5 intermediary tissues of kuhnt
What is the intermediary tissue of kuhnt?
Glial tissue that separates outer retina bundles of optic nerve fibers
What is the internal limiting membrane of the retina?
A layer formed by the footplates of muller cells and is continuous with the inner limiting membrane of elsching
What is Bergmeister’s papillae?
A remnant of meniscus of kuhnt tissue surrounding the hyaloid vasculature during development
Why is bergmeister’s papillae important?
It is responsible for the resorption of the glial tissue that determines the optic cup size at birth
Does the myelination of the optic nerve occur pre or post laminar in the optic nerve?
Post-laminar
What is responsible for the increase in diameter of the retrobulbar optic nerve?
The tissue wrapped around the nerve
Why are astroyctes important?
-astrocytes form thick columns that keep the axons organized onto bundles in the optic nerve
How are astrocytes identified histologically in the optic nerve?
By their nuclei forming long columns between axonal bundles
How long is the intraorbital portion of the optic nerve?
About 25 mm from sclera to the apex of the orbit
What are the layer so the optic nerve sheath? Why are they important? Where do they go?
-dura mater, arachnoid mater, pita mater
-they are continuous with the meninges around the brain
-all three layers fuse with the skull
What is papilledema?
-bilateral swelling of the optic disc caused by increased intracranial pressure in the subarachnoid space
How does papilledema present?
-Indistinct optic disc margins
-engorged venous blood vessels
-small peripapillary hemorrhage
-loss of spontaneous venous pulsation
What is pseudopapilledema? How does it differ from papilledema?
-buried optic disc drusen
-mucopolysaccharide and protein material that become calcified with age
What is the length of the intracanalicular portion of the optic nerve?
5mm
What bony opening does the intracanalicular portion of the optic nerve pass through?
Optic canal
Where is the ophthalmic artery in relation to the optic nerve in the optic canal?
Inferolateral to the optic nerve
Does the optic nerve course inside or outside the common annular tendon?
INSIDE DUH WE KNOW THIS
What happens at the intracranial portion of the optic nerve? How long is it?
10mm long, it passes within the subarachnoid space and merges with the contralateral side to form the chiasm
What happens to visual information at the optic chiasm?
It merges with visual information from the contralateral side
Where is the optic chiasm located?
In the floor of the third ventricle
What blood vessels pierce the optic nerve?
Central retinal artery and vein
What supplies the retinal layer of the optic disc? Is that vessel fenestrated or non-fenestrated?
Retinal capillaries, non-fenestrated
How and where does the choroidal layer get nutrients?
Only the peripheral portion of the laminate choroidal is receives nutrition via diffusion from surrounding choroidal vasculature
What supplies the laminate cribrosa and the adjacent pial plexus?
Arterial circle of zinn-haller (which is supplied by SPCA)
Is there a connection between retinal and posterior ciliary arterial systems?
No
How does the central retinal artery enter the eye?
An aperture in the laminate cribrosa of the optic disc
How is the central retinal artery positioned in relation to the optic nerve and central retinal vein?
Slightly nasal in the nerve and nasal to central retinal vein
What is the ISNT rule?
The neuroretinal rim widths From thickest to thinnest: inferior, superior, nasal, temporal
