Lesions of the Visual System- Graf Flashcards
Pathway lesions are very clear cut. Cognitive lesions are not so clear cut
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Patches in diabetic retinopathy
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Glaucoma can be monocular (primarily) or biocular
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What is scotoma?
loss of a part of the visual field
What is nyctalopia?
poor night vision (with extreme myopia, cataract, vitamin A deficiency)
What is diplopia?
double vision
What is photopic vision?
daylight- cone (color) vision
What is scotopic vision?
night-rod (black/white) vision
What are the normal limits of the visual field?
160 degrees horizontally
135 degrees vertically
The right visual hemifield corresponds to?
right nasal retina and left temporal retina
The left visual hemifield corresponds to?
left nasal retina and right temporal retina
What are the optic radiations?
The optic radiation (also known as the geniculocalcarine tract, the geniculostriate pathway, and posterior thalamic radiation) are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex.
The optic radiations can be divided into what two pathways?
retrolenticular pathway
sublenticular pathway or the “temporal detour”
The optic radiations can be divided into what two pathways?
retrolenticular pathway
sublenticular pathway or the “temporal detour”
What is the Meyer’s loop?
they are fibers from the superior retina
What fibers do the retrolenticular pathway represent?
fibers representing superior retinal quadrants
What fibers do the sublenticular pathway represent?
fibers representing inferior retinal quadrants
Describe the projection of input from the retina to the visual cortex.
The inferior halves of the retina receives what information from the visual hemifields? Where is this information transmitted to in the primary visual cortex?
- information from the superior visual hemifields
- information is transmitted via MEYER’S LOOP to the inferior banks (lingual gyrus) of the primary visual cortex
Describe the projection of input from the retina to the visual cortex.
The superior halves of the retina receives what information from the visual hemifields? Where is this information transmitted to in the primary visual cortex?
- information from the inferior visual hemifields
- information is transmitted to the superior banks (cuneus gyrus) of the primary visual cortex
If there is lesion of the right optic nerve, how is the visual field disrupted?
right eye blindness
If there is lesion of the right optic nerve, how is the visual field disrupted?
right eye blindness AKA
monocular blindness
If there is a coronal lesion of the optic chiasm, how is the visual field disrupted?
complete blindness
If there is lesion in the left optic tract?
right temporal and left nasal region is affected AKA
bilateral right hemianopia
If there is lesion in the left optic tract, how is the visual field affected?
right temporal and left nasal region is affected AKA
bilateral right hemianopia AKA contralateral homonymous hemianopsia
If there is a lesion in right Meyer’s loop, how is the visual field affected?
loss of vision in the superior quadrant of the contralateral (left) half of the visual field for both eyes AKA
upper contralateral (left) quadrantic anopsia
If there is partial lesion in the visual cortex in the lower left bank of the calcarine sulcus, how is the visual field affected?
deficit in the superior quadrant of the contralateral (right) visual field
If there is partial lesion in the visual cortex in the upper right bank of the calcarine sulcus, how is the visual field affected?
deficit in the inferior quadrant of the contralateral (left) visual field
If there is lesion involving both banks of the calcarine sulcus, how is the visual field affected?
contralateral homonymous hemianopsia, however sparing the foveal representation
Why might macular vision be spared after posterior cerebral artery occlusion?
because of the dual blood supply of the primary visual cortex by the posterior and middle cerebral arteries
Visual processing centers in the cerebral cortex are organized in two pathways: a dorsal stream and a ventral stream. What do each streams represent?
dorsal stream: motion, depth, spatial information
ventral stream: object vision, form, color
What is spatial hemineglect?
RIGHT-sided parietal-temporal lobe lesion: TPO junction):
TPO= temporal, parietal, occipital
patients ignore their entire left visual world
What is thought to be involved in causing neglect?
temporal-parietal-occipital junction
What is Balint syndrome?
(bilateral parietal-temporal lobe lesions): spatial-temporal disorientation, generalized loss of attention, combining paralysis of visual fixation, optic ataxia, and impairment of visual fixation, inability to execute voluntary movement in response to visual stimuli
What is visual agnosia?
deficit in object perception while vision is preserved
lesions are in the temporal lobe as well as at the temporal-occipital border
What is achromatopsy?
- loss of color vision
- lesion of area V4
What is prosopagnosia?
- a loss of the ability to recognize faces
- lesion in the LEFT temporal lobe
-after particular lesions of the RIGHT temporal lobe, the ability to recognize faces is preserved, however the patients are unable to gage the emotional content of facial expressions
What is alexia?
the loss of ability to read
-lesion of the left occipital cortex or of the angular gyrus
What is akinematopsy?
loss of perception of motion
lesion of area V5 (MT, MST)
