Visual Lesion Localization Flashcards
how do images on the retina form?
inverted and reversed
info from the upper visual field is projected on the lower retina, R visual field is project on the L hemiretina
where does the central fixation point fall?
on the fovea
what creates the blind spot? where is it located?
optic disc
lateral to the macula
what is the visual field?
total area seen by the combined visual field of both eyes
how can the retina be divided?
by a vertical line, divides fovea and retina into two halves
nasal and temporal
what is the monocular zone?
portion of the visual field that comes from only one eye, temporal crescent of the visual field projects to the nasal hemiretina
what decussated in the optic chiasm?
visual information from the nasal hemiretinae
what does each optic tract contain?
axons from the contralateral nasal hemiretina and ipsilateral temporal hemiretina
stimuli from one visual hemifield are…
processed in the contralateral thalamus and cerebral cortex
inferior optic radiations path
arc forward from thalamus into the temporal lobe near the inferior horn of the lateral ventricle to lingual gyrus
Meyer’s loop, info from the inferior retina
upper optic radiations path
from thalamus, pass under parietal lobe to cuneus gyrus
info from the superior retina
what are the two types of positive visual phenomena?
simple and formed
what are examples of simple positive visual phenomena? what are some causes?
flashes, lights, colors, shapes
retinal detachment, glaucoma, migraines, occipital seizure
what are examples of formed positive visual phenomena? what are some causes?
hallucinations of people/animals, complex scenes
focal seizures, complex migraines, neurodegenerative disorders, toxic disturbances, withdrawal
what do formed positive visual phenomena arise from?
inferior occipitotemporal visual association cortex
what is the release phenomenon?
formed visual hallucinations in an area of visual field loss
what is a monocular scotoma? where is the lesion?
defined region of visual loss in a portion of one eye
retina
what is monocular visual loss? where is the lesion?
loss of vision from one entire eye
optic nerve
what is bitemporal hemianopia? where is the lesion?
loss of temporal visual fields bilaterally (loss of nasal retina info bilaterally)
optic chiasm
what is contralateral homonymous hemianopia? where is the lesion?
injury to the same regions of the visual fields for both eyes
optic tract, lateral geniculate nucleus, entire optic radiation, or entire primary visual cortex unilaterally (DGH)
what is contralateral superior quadrantanopia? where is the lesion?
“pie in the sky”
Meyer’s loop or lower bank of calcarine fissure (EJ)
what is contralateral inferior quadrantanopia? where is the lesion?
“pie on the floor”
parietal lobe interrupting upper optic radiations or upper bank of calcarine fissure
what can result in macular sparing?
partial lesions of the visual field because the fovea has a large representation throughout the pathway
what can the MCA or PCA do in a lesion of the visual cortex?
provide collateral blood supply to the macular region of the visual cortex
what is an altitudinal scotoma? where is the lesion?
upper or lower retina loss
occlusion one of two major branches of the central retinal artery
what can cause binocular altitudinal scotoma?
disease of the basilar artery
where do a minority of fibers in the optic tracts go?
bypass lateral geniculate nucleus to go to the bronchium of the superior colliculus
what are projections to the pretectal area* and superior colliculus important for?
directing visual attention and eye movements toward visual stimuli
pupillary light reflex*
where does the pretectal area and superior colliculus project to?
association cortex via relays in the pulvinar and lateral posterior nucleus of thalamus
the pupillary light reflex is under what type of control
parasympathetic
pupillary light reflex pathway
light activates retinal ganglion cells, project to both optic tracts to brachium of superior colliculus, synapse in pretectal area
axons project bilaterally to Edinger-Westphal nucleus synapse on preganglionic parasympathetic neuron
pregang fibers travel bilaterally in CN III to synapse on postgang para neurons in the ciliary ganglion
postgang fibers to pupillary constrictor muscles
direct vs consensual response
direct - same eye with light shone in it
consensual - opposite eye
pupil dilation is under what kind of control?
sympathetic
pupil dilation pathway
dorsal visual processing pathway
“where?” pathway to parieto-occipital association cortex
motion and spatial relationships between objects and self
ventral visual processing pathway
“what?” pathway to occipitotemporal association cortex
analyzing form, with specific regions for colors, faces, letters
cortical blindness
bilateral damage to primary visual cortex
lack insight into disease (anosognosia)
dismiss diagnosis, confabulate visions
what can inferior occipitotemporal cortex damage cause?
prosopagnosia, achromatopsia, micropsia
what is Balint’s syndrome?
bilateral damage to dorsolateral parieto-occipital cortex
simultanagnosia, optic ataxia, ocular apraxia
prosopagnosia
inability to recognize faces, bilateral fusiform gyrus damage
achromatopsia
central disorder of color perception; can’t name, point to, or match colors presented visually
can name/recall appropriate color of objects verbally
micropsia
objects appear unusually small or large
simultanagnosia
impaired ability to perceive parts of a visual scene as a whole; perceived area shifts unpredictably
optic ataxia
impaired ability to reach for or point to objects under visual guidance; proprioception is intact though, can reach for an object once it has been touched
ocular apraxia
difficulty voluntarily directing one’s gaze toward objects in the periphery through saccades
