functional neuroanatomy of vision W5

Question 1

what are visual fields

Answer 1

the overall fields of vision where both inputs from both orbits are combined

Question 2

describe the organisation of the visual pathways.

Answer 2

light enters eyes, lands on temporal/nasal portions of retina. signals from retina are transmitted via the optic nerve. decussation occurs as the optic chiasm and fibres from the nasal portion cross over. fibres from contralateral visual fields combine to travel up the optic tract to the lateral geniculate body. fibres from lower and upper visual fields separate to reach occipital cortical areas in the optic radiation

Question 3

monocular blindness presentation and defect location?

Answer 3

monocular blindness presents as complete blindness in one eye.
defect in eye or optic nerve

Question 4

bitemporal hemianopia presentation and defect location?

Answer 4

blindness in outer visual fields - aka nasal portion in retina
defect in optic chiasm

Question 5

what do pituitary tumours often cause

Answer 5

bitemporal hemianopia

Question 6

homonymous hemianopia presentation and defect location?

Answer 6

blindness in one side of visual field in both eyes
defect in optic tract

Question 7

superior homonymous quadrantanopia presentation and defect location?

Answer 7

blindless in upper left or right parts of the visual field in both eyes.
defect in the lower fibres of the optic radiation

Question 8

inferior homonymous quadrantanopia presentation and defect location?

Answer 8

blindness in lower left or right parts of the visual field in both eyes.
defect in the upper fibres of the optic radiation

Question 9

homonymous hemianopia with macular sparing defect location?

Answer 9

defect in occipital cortex in higher up areas of optic radiation

Question 10

right visual field defects means lesion in which hemisphere?

Answer 10

left hemisphere - other than monocular blindness as this is before fibres decussate

Question 11

optic nerve anatomical features

Answer 11

travels alongside retinal vessels within the optic sheath to reach and innervate the retina
enters the eye at the optic disc
optic nerve is a myelinated tract of the CNS, encased in meninges. this allows it to act as a window to the brain

Question 12

2 layers of the retina?

Answer 12

neurosensory retina
retinal pigment epithelium

Question 13

neurosensory retina function?

Answer 13

contains specialised neurons for phototransduction

Question 14

neurons in neurosensory retina? features?

Answer 14

rods - high sensitivity, low acuity, no colour
cones - low sensitivity, high acuity, red/green
ganglion - blue, circadian rhythm

Question 15

retinal pigment epithelium features?

Answer 15

maintain overlying neurosensory layer
absorbing scattered light
blood/eye barrier

Question 16

what input does the primary visual cortex receive

Answer 16

visual signals from the contralateral visual field.
eg left visual field to right pvc

Question 17

higher visual centres?

Answer 17

dorsal stream
ventral stream

Question 18

dorsal stream?

Answer 18

posterior parietal cortex
‘where/how’ pathway
integrates vision with motor/sensation

Question 19

ventral stream?

Answer 19

inferior temporal cortex
‘what’ pathway
form regocni

Question 21

what location of lesions causes visual agnosia

Answer 21

occipital and/or temporal lobes

Question 21

types of visual agnosia

Answer 21

prosopagnosia - unable to recognise familiar faces
associative visual agnosia - unable to name things visually

Question 22

conjugate eye movements- inputs, outputs, connection?

Answer 22

input - visual cortex, cerebellum, vestibular nuclei (balance input), superior colliculus
output - horizontal and vertical gaze centres in pons and midbrain coordinate output to cranial nerve nuclei bilaterally
connected by medial longitudinal fasciculus (MLF)

Question 23

name for when eyes dont move together? what is this caused by?

Answer 23

dysconjugate ocular movements
caused by lesion in medial longitudinal fasciculus (MLF)