Intro and Optic Nerve Anatomy

Question 1

Do field defects become more or less congruous the further back we go in the visual system?

Answer 1

more congrous

Question 2

What forms the optic nerve?

Answer 2

Retinal ganglion cells

Question 3

What are two cell bodies in the INL?

Answer 3

bipolar cells, muller cells

Question 4

What type of cells do rods/ cones synapse with?

Answer 4

bipolar

Question 5

which nerve fiber bundle goes from the fovea into the optic nerve?

Answer 5

papillo-macular bundle

Question 6

1/3 of afferent fibers serve what portion of the visual field?

Answer 6

central 5 degrees; central vision is exaggerated the further back we go in the visual system- more cells dedicated to central vision than peripheral

Question 7

where do the neurons of the optic nerve begin (most distal portion of a RGC)

Answer 7

Inner plexiform layer

Question 8

What is another name for the lamina cribrosa?

Answer 8

scleral canal

Question 9

when does the optic nerve become myelinated?

Answer 9

after it passes through the lamina cribrosa

Question 10

RGC axons bundles and supporting astrocytes are located where?

Answer 10

surface and prelaminar RNFL

Question 11

The optic nerve is structurally part of the CNS/PNS

Answer 11

CNS (oligodendrocytes create the myelin sheaths); other cranial nerves are mostly PNS

Question 12

What is the innermost surrounding layer of the optic nerve?

Answer 12

pia mater (vascular)

delicate

Question 13

What is the outer sheath of the optic nerve?

Answer 13

arachnoid mater and dura mater

Question 14

What is the subarachnoid space continuous with?

Answer 14

cerebral subarachnoid space (contains CSF)

Question 15

What makes up the circle of Zinn-Haller? (the arterial vascular supply of the optic nerve)

Answer 15

All derived from the ophthalmic artery:
1. Short posterior ciliary arteries (supply the choroid)
2. Choroidal vessels
3. Pial (meningeal) vessels

Question 16

What exits the orbit via the optic canal?

Answer 16

Optic nerve, ophthalmic artery and sympathetic fibers

Question 17

What runs along-side the intracranial optic nerve/ chiasm?

Answer 17

internal carotid

Question 18

What passes through the cavernous sinus?

Answer 18

CN III, IV, V1, V2, VI, ICA and sympathetics

Optic nerve, chiasm and tracts do NOT pass throught the cavernous sinus

Question 19

What synapses at the LGN?

Answer 19

RGC axons

Question 20

Where do the LGN axons synapse?

Answer 20

striate cortex (V1)

Question 21

What layers contain portions of retinal ganglion cells

Answer 21

IPL, GCL, RNFL

Question 22

What is the lamina criborosa made of?

Answer 22

beams of connective tissue

filled with axons and glia to make a tight seal

IOP on one side, cerebrospinal fluid pressure other side; the two don’t mix

Question 23

how do we identify which eye we are looking at on an OCT?

Answer 23

looking at build up of RNFL as you get closer to the optic

Question 24

What vein is responsible for drainage of optic nerve head?

Answer 24

Central retinal vein

Question 25

What is the primary route of drainage from the optic nerve head?

Answer 25

Central Retinal Vein-> Superior Ophthalmic Vein -> Cavernous Sinus -> Petrosal Sinuses (sup and inf) -> Internal jugular -> subclavian vein -> Brachiocephalic veins (L or R) -> superior vena cava

Question 26

How long is the optic nerve from the globe to the chiasm?

Answer 26

50 mm

Question 27

Which is the longest section of the optic nerve? Where does it run?

Answer 27

Intraorbital; runs from globe to orbital apex (optic foramen) ## Footnote addition of myelin here; surrounded by annular/ tendinous ring of Zinn

Question 28

Which section of the optic nerve contains the optic nerve head and is where the axons pass through lamina cribrosa?

Answer 28

intraocular

Question 29

Which segment of the optic nerve traverses the optic canal?

Answer 29

Intracanalicular | the nerve is fixed to the canal; dura mater is fused here

Question 30

Which segment is vulnerable to damage from adjacent lesions like adenomas or aneurysms?

Answer 30

Intracranial

Question 31

What are the 4 segments of the optic nerve?

Answer 31

1.Intraocular 2. Intraorbital 3. Intracanalicular 4. Intracranial

Question 32

What structure houses the pituitary gland?

Answer 32

sella turcica

Question 33

What sits on top of sella turcica?

Answer 33

Optic chiasm

Question 34

What makes up the optic tract?

Answer 34

the nasal crossing fibers and the temporal ipsilateral fibers

Question 35

What is the blood supply for the optic tracts?

Answer 35

Branches of the posterior cerebral artery and anterior choroidal artery ## Footnote branch off internal carotid artery

Question 36

What are the four synaptic targets of the Optic Tract?

Answer 36

1. LGN: form vision; efferent sensory; RGC axons synapse on LGN cells; axons synapse at striate cortex (V1) 2. Suprachiasmatic Nucleus: hypothalamus is here; circadian rhythms; from intrinsically photosensitive RGC's 3. Pretectal Nucleus: Pupil; from intrinsically photosensitive RGC's 4. Superior Colliculus: (midbrain) saccades; orienting eye movement