Optic radiations Flashcards
What is another name for the optic radiations?
geniculocalcarine tracts
What do the optic radiations consist of?
nerve fibre bundles whose cell bodies lie in the LGN
Where do the axons of nerve fibres in the optic radiations terminate?
in the visual (striate) cortex
What is the path of the optic radiations?
- fibres form a wide forward and inferiorly directed fan-shaped loop (of Meyer)
- first pass into the retrolenticular portion of the internal capsule (posterior to sensory fibres and medial to auditory fibres)
- then fibres pass into temporal lobe around inferior horn of lateral ventricle
- each tract passes posteriorly along lateral aspect of posterior horn of lateral ventricle
- then turn medially to enter visual cortex
Where are the fibres of the optic radiations located in the internal capsule compared with other fibres?
posterior to sensory fibres, medial to auditory fibres
Why are the optic radiations of major clinical importance?
frequently involved in cerebrovascular disturbance or tumours
Do all fibres of the optic radiations loop to the same degree?
no
What causes the degree of loop in the optic radiations of different fibres to vary?
those destined for the lower half of the visual cortex take a wider sweep into the loop around the tip of the inferior horn of the lateral ventricle (see pic) than those destined for the upper half of the visual cortex
Which part of the retina are optic radiation fibres that take the furthest swing into the loop associated with?
furthest swing into the loop = peripheral retina
those passing more directly posteriorly = closer to or within macula region