Intro and Optic Nerve Anatomy Flashcards
Do field defects become more or less congruous the further back we go in the visual system?
more congrous
What forms the optic nerve?
Retinal ganglion cells
What are two cell bodies in the INL?
bipolar cells, muller cells
What type of cells do rods/ cones synapse with?
bipolar
which nerve fiber bundle goes from the fovea into the optic nerve?
papillo-macular bundle
1/3 of afferent fibers serve what portion of the visual field?
central 5 degrees; central vision is exaggerated the further back we go in the visual system- more cells dedicated to central vision than peripheral
where do the neurons of the optic nerve begin (most distal portion of a RGC)
Inner plexiform layer
What is another name for the lamina cribrosa?
scleral canal
when does the optic nerve become myelinated?
after it passes through the lamina cribrosa
RGC axons bundles and supporting astrocytes are located where?
surface and prelaminar RNFL
The optic nerve is structurally part of the CNS/PNS
CNS (oligodendrocytes create the myelin sheaths); other cranial nerves are mostly PNS
What is the innermost surrounding layer of the optic nerve?
pia mater (vascular)
delicate
What is the outer sheath of the optic nerve?
arachnoid mater and dura mater
What is the subarachnoid space continuous with?
cerebral subarachnoid space (contains CSF)
What makes up the circle of Zinn-Haller? (the arterial vascular supply of the optic nerve)
All derived from the ophthalmic artery:
1. Short posterior ciliary arteries (supply the choroid)
2. Choroidal vessels
3. Pial (meningeal) vessels
What exits the orbit via the optic canal?
Optic nerve, ophthalmic artery and sympathetic fibers
What runs along-side the intracranial optic nerve/ chiasm?
internal carotid
What passes through the cavernous sinus?
CN III, IV, V1, V2, VI, ICA and sympathetics
Optic nerve, chiasm and tracts do NOT pass throught the cavernous sinus
What synapses at the LGN?
RGC axons
Where do the LGN axons synapse?
striate cortex (V1)
What layers contain portions of retinal ganglion cells
IPL, GCL, RNFL
What is the lamina criborosa made of?
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
how do we identify which eye we are looking at on an OCT?
looking at build up of RNFL as you get closer to the optic
What vein is responsible for drainage of optic nerve head?
Central retinal vein
What is the primary route of drainage from the optic nerve head?
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
How long is the optic nerve from the globe to the chiasm?
50 mm
Which is the longest section of the optic nerve? Where does it run?
Intraorbital; runs from globe to orbital apex (optic foramen)
addition of myelin here; surrounded by annular/ tendinous ring of Zinn
Which section of the optic nerve contains the optic nerve head and is where the axons pass through lamina cribrosa?
intraocular
Which segment of the optic nerve traverses the optic canal?
Intracanalicular
the nerve is fixed to the canal; dura mater is fused here
Which segment is vulnerable to damage from adjacent lesions like adenomas or aneurysms?
Intracranial
What are the 4 segments of the optic nerve?
1.Intraocular
2. Intraorbital
3. Intracanalicular
4. Intracranial
What structure houses the pituitary gland?
sella turcica
What sits on top of sella turcica?
Optic chiasm
What makes up the optic tract?
the nasal crossing fibers and the temporal ipsilateral fibers
What is the blood supply for the optic tracts?
Branches of the posterior cerebral artery and anterior choroidal artery
branch off internal carotid artery
What are the four synaptic targets of the Optic Tract?
- LGN: form vision; efferent sensory; RGC axons synapse on LGN cells; axons synapse at striate cortex (V1)
- Suprachiasmatic Nucleus: hypothalamus is here; circadian rhythms; from intrinsically photosensitive RGC’s
- Pretectal Nucleus: Pupil; from intrinsically photosensitive RGC’s
- Superior Colliculus: (midbrain) saccades; orienting eye movement
