Optic Nerve Anatomy and Development

Question 1

The intraocular ON contains what type of axons of ganglion cells?

Answer 1

Unmyelinated

Question 2

The Arcuate fibers are found where?

Answer 2

Temporal

Question 3

The Cuneate Fibers are found where?

Answer 3

Nasal

Question 4

The Papillomacular bundles extends from what 2 points?

Answer 4

Extends from ONH to macula

Question 5

The horizontal raphe seperates what?

Answer 5

Superior and Inferior

Question 6

What is the importance of the retrolaminar portion on the intraocular ON?

Answer 6

In this area, the thickness of the ON doubles due to myelination of axons by oligodendrocytes

Question 7

The Intraorbital ON is how long and extends from what 2 points?

Answer 7

20-30mm long (longest area)

extends from globe to optic foramen

Question 8

What is the shape of the intraobital ON? Why?

Answer 8

Shape = S-shape because of EOM movements

Question 9

What is the most important characteristic of the intraorbital ON?

Answer 9

Contains meningeal sheaths! Dura, pia mater, and arachnoid layers!

Question 10

What 2 important vessels piece through the sub-arachnoid space in the intraorbital ON? What are these vessels susceptible to?

Answer 10

The CRA and CRV

Increased intracranial pressure.. possible CRA/CRV occlusion

Question 11

The intracanalicular ON runs posterior-medial to what bone?

Answer 11

Lesser wing of sphenoid bone

Question 12

Which portion of the ON extends posterior and medially to reach chiasm?

Answer 12

Intracranial ON

Question 13

What are the 3 blood sources to the NFL?

Answer 13

CRA (main supply), Choroidal Artery and Cilioretinal Artery (not found in everyone)

Question 14

What is the blood supply to the prelaminar area?

Answer 14

Short Posterior Ciliary Arteries

Question 15

What are the 2 sources of blood for the Laminar Area?

Answer 15

Transverse = Circle of Zin-Haller (main supply)

Longitudinal = CRA

Question 16

What are the blood sources for the Retrolaminar blood supply? (has the most blood supply out of all)

Answer 16

• Pia Mater Vascular Plexus
• Retrograde feed from Ciliary Arteries
• Branches from CRA
• Muscular Branches

Question 17

Where do ganglion cell axons, glial support and myelina arise from?

Answer 17

Neural Ectoderm

Question 18

Where does connective tissue support, meninges and lamina cribrosa arise from?

Answer 18

Neural Crest

Question 19

What is the tissue of origin for the blood supply?

Answer 19

mesoderm

Question 20

Axons fill the optic stalk by the 7th week and grow toward the LGB. Which axons will develop first?

Answer 20

The cross nasal (cuneate) fibers (6th - 7th week)

Question 21

During the 11th week, which fibers reach the LGB?

Answer 21

The uncrossed temporal (arcuate) fibers

Question 22

After the temporal axons reach the LGB, myelination begins. What structure gets myelinated first? (and state time of development)

Answer 22

5 mo: LGB
6 mo: Optic Tract
6-7mo: Optic Chiasm
8 mo: Optic Nerve
9 mo: Lamina Cribrosa

Question 23

When does the optic radiations (LGB to cortex) become myelinated

Answer 23

birth to 4 months post-natal

Question 24

What are the anomalies of the ONH?

Answer 24

Myelinated Nerve fibers, ON Aplasia, ON Hypoplasia, Megalopapilla, Congenital Optic Pits

Question 25

Describe Myelinated Nerve Fibers.

Answer 25

Oligodendrocytes surpass lamina cribrosa and myelinate axons in the retina

Question 26

Describe ON Aplasia.

Answer 26

• Without an ON, disc, nothing

- Very rare! Failure to thrive; results in death

Question 27

Describe ON Hypoplasia.

Answer 27

• Failure of Ganglion cell layer to develop
• small hypoplastic disc
• outer ring that shows where ON should be

Question 28

Describe Megalopapilla.

Answer 28

• Large ONH, disc is greater than 2.1 mm
• Normal disc = 1.5 mm
• Bilateral, Healthy Neural Retinal Rim

Question 29

Describe Congenital Optic Pitts.

Answer 29

• Pigmented oval or round depression in the optic disc
• Usually occurs temporally
• Pigment = gray or olive green, white or yellow