Visual Pathways Flashcards
which parts of the eye are responsible for refraction?
cornea- majority of refraction
lens- modifies refraction to focus light on the retina, changes shape to focus on near and far objects
what muscles are responsible for changing the shape of the lens?
cilliary muscles
what is the binocular field?
the area at which the visual fields of both eyes overlap when focusing on an object
why is binocular vision important?
it allows depth perception, hand eye co-ordination and an enlarged visual field
what is the basic visual pathway?
retina -> optic nerve -> optic chiasm -> optic tract -> LGN -> optic radiation -> striate cortex
what happens at the optic chiasm?
the optic nerves come together and some of the axons decussate
everything from the right visual field (right nasal retina and left temporal retina) moves to the left side and vice versa
which layers of the LGN receive input form the contralateral eye?
layers 1,4 and 6
left LGN layers 1,4 and 6 will receive axons from the right eye
what part of the visual field do the lateral fibres (mayers loop) of the optic radiation carry information from?
the lateral fibres carry information from the inferior retinal field which receives information from the superior visual field
what part of the brain do the lateral fibres of the optic radiation pass through?
the temporal lobe
what part of the brain do the medial fibres of the optic radiation pass through?
parietal lobe
where is the striate/primary visual cortex found?
occipital lobe
what cells do layers 1 and 2 of the LGN receive axons from?
they are magnocellular and receive axons from M ganglion cells which are concerned with moving images and contrast
which pathway from the striate cortex is an extension of the parvocellular pathway?
the ventral stream is an extension of the parvocellular pathway and is concerned with the details of vision
what is the consensual pupil response?
pupil constricts due to light being directed into the opposite eye
what does optical accomodation require?
convergence- contraction o the medial rectus muscles to move the eyes medially
pupil constriction
lens thickening- via contraction of the cilliary muscles
