Optic Nerve Q And A Sesh

Question 1

Why does the RNFL run in the direction that it does

Answer 1

-the axons of the ganglion cells have to run parallel to the surface of the retina to converge into the optic nerve

Question 2

How do axons of the ganglion cells differ from the axons of the bipolar cells

Answer 2

Axons of bipolar cells synapse locally, ganglion cells synapse in the LGN

Question 3

Explain why there is a demarcation around the macular area

Answer 3

• it is densely packed with cones, and no rods
• sloped because of Henley fibers
• peripheral retina develops after the central retina so the fibers have to pass around the macula
• avascular
• more than one layer of the RGL
• less layers so the RPE is more visible through
• high levels of carotenoids

Question 4

Explain why the optic disc if longer vertically than it is horizontally

Answer 4

• more to handle on the top and bottom, the ganglion axons have much more coming into the top and bottom of the optic nerve
• very few horizontal fibers that come in, this is why the horizontal sides are thinner

Question 5

Why are all these border glial tissues necessary

Answer 5

• glial cells provide support and maintain environment
• separates the choroid from the optic nerve
• blood brain barrier
• wants to keep things out of the optic nerve so as not to block electric signal

Question 6

Explain how this myelin gets onto the retinal surface

Answer 6

• pre laminar axons myelinated with oligodendrocytes coming into the lamina cribrosa from the myelin surrounding the optic nerve when they normally should not
• if there is myelin it wil be too bulky and could effect vision if too much
• birthmark

Question 7

Explain why the optic nerve becomes thicker once the NFL passes though the lamina cribrosa

Answer 7

• myelination
• optic sheath (pia, arachnoid, dura mater)
• CRA and CRV are in there
• astrocytes form thick columns that keep the axonal fibers organized into bundles in the optic nerve (multiple layers, traffic cops, main role is support)

Question 8

With regards to the dural covertins, compare this cross section of the optic nerve to a cross section of the brain or spinal cord

Answer 8

• looks the same
• pia attached to structure
• Sam organization
• both have CSF in the subarachnoid space
• optic nerve meninges merge with the sclera
• the nptic nerve has the CRA and CRV in the middle of it, the brain does not have anything like that running though it
• optic nerve is both white and gray matter depending on where it is

Question 9

Explain the anatomy of papilledema

Answer 9

• increases CSF causing the disc to bulge out
• veins are engorged because the blood cannot exit the eye (they are compressed mainly where they enter the optic nerve in the subarachnoid space)
• axonal flow gets obstructed

Question 10

Discuss the total blood supply to the optic nerve beginning with the ICA

Answer 10

ICA-opthalmic artery-CRA-caps and short posterior artery

• ophthalmic runs through the canal with the optic nerve
• CRA branches after the optic canal in the intraorbital region, pierces the meninges, runs in the subarachnoid space, then pierces to get into the nerve
• caps branch from the CRA and feed the optic nerve
• short posteiror ciliary artery contribute to the circle of Zinn Haller
• collateral branches of Pial branches from off of this circle whihc give off more caps

Question 11

Describe what is wrong with this optic nerve appearance

Answer 11

FNL

• funny looking nerve
• this is something you document and then just monitor to make sure there are no changes over time with it