Optic radiations

Question 1

What is another name for the optic radiations?

Answer 1

geniculocalcarine tracts

Question 2

What do the optic radiations consist of?

Answer 2

nerve fibre bundles whose cell bodies lie in the LGN

Question 3

Where do the axons of nerve fibres in the optic radiations terminate?

Answer 3

in the visual (striate) cortex

Question 4

What is the path of the optic radiations?

Answer 4

• 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

Question 5

Where are the fibres of the optic radiations located in the internal capsule compared with other fibres?

Answer 5

posterior to sensory fibres, medial to auditory fibres

Question 6

Why are the optic radiations of major clinical importance?

Answer 6

frequently involved in cerebrovascular disturbance or tumours

Question 7

Do all fibres of the optic radiations loop to the same degree?

Answer 7

no

Question 8

What causes the degree of loop in the optic radiations of different fibres to vary?

Answer 8

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

Question 9

Which part of the retina are optic radiation fibres that take the furthest swing into the loop associated with?

Answer 9

furthest swing into the loop = peripheral retina

those passing more directly posteriorly = closer to or within macula region