17 - the visual pathway

what is visual field

everything you can see with one eye

what is binocular vision

everything seen with 2 eyes - larger visual field and perception of depth

how is visual field tested

confrontation test - think of eye ASMR videos

automated perimetry - point and dots

how are images of objects formed within retina

fibres pass through optic nerve to optic chiasma

fibres cross to opposite side at chiasma

enter middle cranial fossa

opposite side visual field

LGB optic radiation passes behind internal capsule to reach occipital lobe

right visual cortex sees left visual field and left visual cortex sees right visual field

lesion - right or left optic nerve damage

blindness in one eye

lesion - optic chiasma disrupted

bitemporal hemianopia - lateral vision vision loss

what can bitemporal hemianopia be caused by

pituitary enlargement

lesion - right optic tract damaged

homonymous hemianopia

- vision loss in each eye - corresponding halves of visual field

- e.g. right visual tract - not able to see left side of visual field

lesion - optic radiation damaged

contralateral homonymous hemianopia