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20 Cards in this Set
- Front
- Back
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What is the point of exit of the optic nerve?
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lamina cribrosa (scleral structure)
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what is papilledema and what is it caused by?
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swelling of the optic disc - caused by high intracranial pressure
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what adverse effect on optic nerve is caused by glaucoma?
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cupping of optic nerve head
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how many optic nerve fibers? where are they myelinated?
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1 million
1 mm behind globe |
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what happens at optic chiasm?
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zone of decussation
temporal retinal fibers remain ipsilateral, nasal fibers go contralateral normal human has ~50% decussation albinos have disruption and only 5-10% decussation |
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what generally happens with a defect in the optic tract? (post chiasma)
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hemianopic field defect
usually congruous and homonymous usually pressure related (tumor) or vascular |
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main recipient of visual input moved from superior colliculus to lateral geniculate body through ??
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evolution
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describe - retino-hypothalamic path
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nuclei receive info from both eyes, mostly from inferior retina
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describe structure of superior colliculus
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layered
superior layer is visual inferior are auditory and somatosensory |
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what is the main function of superior colliculus?
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- orients gaze and attention
- target localization, stabilization of head during head/eye movements |
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describe structure of lateral geniculate body and where does the blood supply come from
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multi layered - magnocellular (1,2), parvocellular (3-6), kiniocellular (interlayers)
dual blood supply - anterior carotid and lateral superior carotid |
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what is Meyer's Loop?
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fibers from inferior retina travel around lateral ventricle
fibers from superior retina go directly to visual cortex |
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describe layers of cerebral cortex?
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layer I: aneuronal; communication
layer II/III: excitatory projections to cortical structures layer IV: granular recipient layer layer V/VI: excitatory projections to subcortical structures (feedback) |
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what is binocularity
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property of cortical cells which receive info from both eyes
requires overlapping visual fields and 2 eyes in frontal position advantages - stereopsis, binocular summation, redundancy of info disadvantages - complex mechanism of vergence |
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what is retinal disparity?
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hemifield images are combined at the visual cortex - normal should have exact retinal correspondence for the object at the point of fixation. disparity occurs for all other objects seen from a different position
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what is the Horopter
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"plan" in visual space which shows areas of retinal correspondence (on the line) and disparity (within or beyond)
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what is Panum's area
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zone of space around Horopter where (even if beyond Horopter) objects are still seen singly, despite the retinal disparity being produced (area of fine stereo)
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Why are disparities possible in Panum's area?
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slight overlapping of vertical meridian
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how can depth perception be attained by monocular clues?
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monocular clues
- linear perspective - interposition - size constancy - texture gradient - shadows - optical flow |
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what are binocular clues to depth perception?
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accommodation and convergence
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