Neuro-Ophthalmology Flashcards
(51 cards)
90% of retinal axons terminate where?
the lateral geniculate nucleus, which is the principal sucbcortical structure that carries visual info to the cerebral cortex through the optic radiations
Where is the primary visual cortex?
Brodmann’s area 17, or striate cortex
Where does the visual information go after the striate cortex, or V1?
the associative visual cortex, areas 18 and 19
If visual acuity is decreased, where is the issue typically localized?
either to the eye’s inherent refractive mechanism (and will improve if you test the VA through a pinhole) or to the optic nerve (and will NOT improve through a pinhole)
Early optic nerve problems can present with difficulty perceiving which color?
red (a particularly common presentation for MS optic neuritis)
How do you test for an afferent pupillary defect (marcus gunn pupil)?
Flash a bright light alternately for 2-3 sec in each eye
if the ipsilateral pupil appears to dilate when the light is directed toward that eye, an afferent pupillary defect is present
What visual defect will occur with right optic nerve damage?
right eye blindness
What visual defect will occur with chiasm pathology?
bitemporal hemianopsia
What visual defect will occur with damage to the right optic tract?
left homonymous hemianopsia
What visual defect will occur with damage to the right parietal optic radiation?
left inferior homonymous quandrantonopia
What visual defect will occur with damage to the right temporal optic radiation?
left superior homonymous quadrantonopia
What visual defect will occur with both optic radiations are damaged?
left homonymous hemianopia (just like with the right optic tract)
What visual defect will occur with damage to the right visual cortex?
left homonymous hemianopia with macular sparing
What is the technical term for unequal pupil size? In what percentage of people can this be normal?
anisocoria
normal in 25%
For the pupillary light reflex, the afferent signal follows the initial visual pathway: retina to optic nerve, chiasm, optic track and then synapses where?
the edinger-westphal nucleus in the rostral aspect of the third nerve nucleus
Efferent fibers from the Edinger-Westphal Nucleus then travel with the third cranial nerve. Are these fibers sympathetics or parasympathetics?
parasympathetics
These parasympathetic fibers ultimately synapse in what ganglion prior to reaching the pupilloconstrictor?
ciliary ganglion (located in the posterior orbit)
The pupillodilator is innervated by sympathetics. Where do these sympathetic fibers start?
in the ipsilateral posterolateral hypothalamus
Where do these sympathetic fibers project to?
they descend down the brainstem to the interomediolateral cell column at the C8-T1 spinal level
The second order neurons go from C8-T1 to synapse in what ganglion?
superior cervical ganglion
The third order sympathetics travel from the superior cervical ganglion to the eye along what structure?
the internal carotid artery into the cavernous sinus
What characterizes Horner’s Syndrome?
ipsilateral miosis (small pupil) ptosis (drooping of upper lid) inverted ptosis (elevation of the lower lid)
and depending on the level of the lesion…
impaired ipsilateral facial flushing and sweating
What effect will cocaine have on the pupil in horner’s syndrome?
cocaine drops will fail to dilate the abnormal pupil (because cocaine inhibits the reuptake of NE from the synaptic cleft, but if the sympathetics aren’t working, this won’t do anything)
Cocaine will fail to dilate the pupil, but what will succeed?
apraclonidine (a weak direct-acting alpha1 and alpha2 agonist that dilates the affected eye due to denervation supersensitivity of the iris dilator muscle)
