optic nerve: anatomy and disorders Flashcards
most common site of traumatic optic neuropathies
blow to the brow - attached to the dura in the optic canal
what do ganglion cells respect in the retina
the horizontal midline
what percentage of gnaglion cells duccusate
53% cross
47% remain on same side
where is common site of optic nerve constriction
lamina cibrosa
what is special about the cup in the disc
devoid of any axons and tissue (white)
what is normal cup to disc ratio
0.3
what is large cup a sign of
glaucoma
5 ways to test optic nerve function
- central visual acuity
- RAPD
- visual fields
- color testing
- contrast sensitivity
what is an RAPD a sign of
optic nerve damage in that eye - most optic neuropathies are assymetric and thus will have an RAPD
3 keys things to assess in the optic nerve clincally
Borders - are they sharp?
Color - pink is normal - is there pallor
Cup - can I see it - ratios
what is papilledema
swelling of the optic nerve head due to increased ICP - usually bilateral
pathophysio of pappiledema
increase ICP>less space for CSF>CSF excess around optic nevre> swelling
when might pappiledema be assymetric
if the nerve is atrophic
what is axoplasmic stasis
increase ICP transmitted to optic nerve along meningeal sheaths - stops axoplasmic flow at lamina cibrosa
what is diff b/w papill and other optic neuropathies
in pap the visual acuity is pretty normal
tests for pappiledma
imaging and if normal > lumbar puncture to meausre pressure and CSF
5 other types of optic neuropathies
- congenital
- inflammatory
- ischemic
- toxic metabolic
- traumatic
2 cats of inflammatory
- infectious - TB, syphillis, virus
2. non-infectious - idopathic, sacroid, Wegners
what is most common optic neuropathies in under/over 50
under - demylenating
over - ischemic
2 types of ischemic
arteritic - rarer, but more devastating
non-arteritic - treatable
Sx of demylenating (3)
- unilateral vision loss
- RAPD
- pain on eye movements
what is relat between optic neuritis and MS
50% will dev. MS - even one lesion is predictive - better MS outcomes though
what is non ateritic ischemia
wake up with vision loss and is often altitidunal - hypoperfusion
what is giant cell arterititis
inflammation of wall of medium size vessels - occludes lumen
