The Optic Nerve Flashcards
Function
Carries visual reflex signals from the retina to the rest of the visual pathway
Location
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
Length of the optic nerve
40-50mm long
3 Meningeal Sheaths
Pia Mater
Arachnoid Mater
Dura Mater
4 Sections of Optic Nerve
Intra-ocular
Intra-orbital
Intracanalicular
Intracranial
Thickness: Intra-ocular
1-1.5mm
Length: Intra-orbital
25mm
Length: Intracanalicular
5-10mm
Length: Intracranial
5-10mm
Blood supply
Circle of Haller-Zinn
Ophthalmic Artery
Central Retinal Artery
Drainage
Drainage is from central retinal vein, basal veins and anterior cerebral vein
Optic nerve contains..
Contains 1.1 – 1.3 million axons from retinal ganglion cells
Intra-ocular (2 features)
Extends from retinal surface to edge of posterior scleral foramen
Different neuroglial cells present
Intra-orbital (2 features)
Extends from globe to optic foramen
Covered in 3 meningeal sheaths of the CNS
Intracanalicular (3 features)
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
Intracranial
Extends from optical canal to middle of cranial fossa
Only pia mater left directly onto optic nerve here
Where does the central retinal artery enter the nerve
10-15mm behind the globe
How is the end of the optic nerve marked
End of nerve marked by end of pial septa
In which point does the dura mater divert away from the nerve to cover the brain
In the Intracranial section
Circle of Haller- Zinn supplies…
area around optic nerve head and is provided by the short posterior ciliary arteries
Ophthalmic Artery
Forms central retina artery where it branches off to support other orbital structures
Central Retinal Artery
1st branch of ophthalmic artery that enters meninges 10-15mm behind the globe
