The Optic Nerve

Question 1

Function

Answer 1

Carries visual reflex signals from the retina to the rest of the visual pathway

Question 2

Location

Answer 2

Starts at the anterior surface of the retina at the optic nerve head

Travels backwards through the lamina cribrosa into the orbit.

Surrounded by the rectus muscles before it reaches the optic foramen in the sphenoid bone.

At the foramen it passes through the optic canal and ends at the anterior border of the optic chiasma

Question 3

Length of the optic nerve

Answer 3

40-50mm long

Question 4

3 Meningeal Sheaths

Answer 4

Pia Mater
Arachnoid Mater
Dura Mater

Question 5

4 Sections of Optic Nerve

Answer 5

Intra-ocular
Intra-orbital
Intracanalicular
Intracranial

Question 6

Thickness: Intra-ocular

Answer 6

1-1.5mm

Question 7

Length: Intra-orbital

Answer 7

25mm

Question 8

Length: Intracanalicular

Answer 8

5-10mm

Question 9

Length: Intracranial

Answer 9

5-10mm

Question 10

Blood supply

Answer 10

Circle of Haller-Zinn
Ophthalmic Artery
Central Retinal Artery

Question 11

Drainage

Answer 11

Drainage is from central retinal vein, basal veins and anterior cerebral vein

Question 12

Optic nerve contains..

Answer 12

Contains 1.1 – 1.3 million axons from retinal ganglion cells

Question 13

Intra-ocular (2 features)

Answer 13

Extends from retinal surface to edge of posterior scleral foramen

Different neuroglial cells present

Question 14

Intra-orbital (2 features)

Answer 14

Extends from globe to optic foramen

Covered in 3 meningeal sheaths of the CNS

Question 15

Intracanalicular (3 features)

Answer 15

At apex of orbit the dura mater divides

Outer layer attached to periorbita and proximal tendon of the rectus muscles to anchor

Inner layer continues through optical canal

Question 16

Intracranial

Answer 16

Extends from optical canal to middle of cranial fossa

Only pia mater left directly onto optic nerve here

Question 17

Where does the central retinal artery enter the nerve

Answer 17

10-15mm behind the globe

Question 18

How is the end of the optic nerve marked

Answer 18

End of nerve marked by end of pial septa

Question 19

In which point does the dura mater divert away from the nerve to cover the brain

Answer 19

In the Intracranial section

Question 20

Circle of Haller- Zinn supplies…

Answer 20

area around optic nerve head and is provided by the short posterior ciliary arteries

Question 21

Ophthalmic Artery

Answer 21

Forms central retina artery where it branches off to support other orbital structures

Question 22

Central Retinal Artery

Answer 22

1st branch of ophthalmic artery that enters meninges 10-15mm behind the globe