Visual Pathway Flashcards
What is the visual field?
Everything you see with one eye (including the periphery)
What is the fovea of the eye?
Tiny pit located in the retina that provides the clearest vision
What kind of tests looks at the visual field?
Confrontation test or automated perimetry, not to be confued with visual acuity testing
How do images of objects in our visual field compared to how we actually interpretate them?
They are upside down and inverted (left and right), so the right visual cortex ees the left half of the visual field and vice versa
Explain the process of the visual pathway?
1) All fibres from the eye pass through the optic nerve to the optic chiasma
2) At the optic chiasma the medial nasal fibres cross to the opposite side
3) So the optic tract contains fibres from the lateral temporal half of the ipsilateral eye and the crossed over nasal fibres from the contralateral eye
4) This corresponds to all fibres from the opposite half of the visual field
5) Fibres from optic tract synapses at the LGB of the thalamus
6) From here the optic radiation passes behind the internap capsule (retro-lentiform fibres) to reach the primary visual cortex in the occipital lobe (area 17)
7) Thus the right visual cortex sees the left half of the visual field and vice versa
What does LGB stand for?
Laterl geniculate body
What fibres cross to the opposite side at the optic chiasma?
Nasal fibres
What fibres does the optic tract contain?
Fibres from the lateral temoral half of the ipsilateral eye and the crosed over nasal fibres from the contralateral eye
What is A?
Optic nerve
What is B?
Optic chiasma
What is C?
Optic tract
In what lobe is the primary visual cortex located?
Occipital lobe
In what area of the brain is the primary visual cortex located?
Area 17
What is the general rule of thumb for where a lesion is in relation to the side of loss of vision?
Is usually in the opposite side from visual loss, but this is not always the cases such as with optic nerve damage
what happens with a lesion in the right optic nerve?
Blindness in one eye (the right)
What happens with a lesion in the optic chiasma disrupted in the middle?
Bitemporal hemianopia
What is bitemporal hemianopia?
Vision missing in lateral temporal half of visual field
What happens with a lesion in the right optic tract?
Homonymous hemianopia (can see one half of each eye, in this case the lateral half of the left eye and the medial half of the right eye)
