3 - Visual Pathways

Question 1

how many rods and cones does the retina contain?

Answer 1

rods - 100 million
cones - 6 million

Question 2

what are the 3 roles of rods?

Answer 2

• vision in low lighting
• peripheral vision
• low resolution

Question 3

what are the 3 roles of cones?

Answer 3

• detailed vision
• colour vision
• brighter light

Question 4

the retina projects to four subcortical regions in the brain - what are they?

Answer 4

• lateral geniculate nucleus - primary visual pathway
• superior colliculus
• hypothalamus
• pretectum

Question 5

what is the course of the fibres in meyer’s loop?

Answer 5

fibres from inferior retina travel through the temporal lobe

Question 6

the straight fibres of the optic radiation contain fibres from which part of the retina?

Answer 6

superior retina

Question 7

the straight fibres of the optic radiation travel through which lobe of the brain?

Answer 7

parietal

Question 8

meyer’s loop fibres travel through what lobe of the brain?

Answer 8

temporal

Question 9

meyer’s loop contains fibres from which part of the retina?

Answer 9

inferior retina

Question 10

the looped part of the optic radiation is called what?

Answer 10

meyer’s loop

Question 11

where is the optic disc in relation to the fovea?

Answer 11

nasal

Question 12

what is the optic disc?

Answer 12

a blind spot in temporal visual field at about 15 degrees eccentricity

Question 13

list a retinal cause of a visual field defect:

Answer 13

• vascular - retinal artery occlusion
• retinal detachment
• macular lesion - central defect

Question 14

list an optic nerve cause of a visual field defect:

Answer 14

• glaucoma
• optic neuritis
• optic atrophy
• optic nerve compression

Question 15

list a lesion at the chiasm that could cause a visual field defect

Answer 15

tumour - esp pituitary

Question 16

list a lesion after the chiasm that could cause a visual field defect

Answer 16

• stroke
• tumour

Question 17

list an occipital cortex cause of visual field defects

Answer 17

• stroke
• trauma

Question 18

visual field abnrmalities that do not cross the midline are of what origin?

Answer 18

retinal

Question 19

macular degeneration causes what sort of visual field defect?

Answer 19

central visual field defect

Question 20

a superonasal retinal detachment in the left eye will cause what visual field defect?

Answer 20

inferotemporal visual field defect

Question 21

a pituitary tumour most often results in what type of visual field defect?

Answer 21

bitemporal hemianopia

Question 22

homonymous hemianopias (retrochiasmal lesions) are named after what?

Answer 22

the eye that has the temporal vision loss

Question 23

what are the two theories of macular sparing?

Answer 23

• macular takes up large area of visual cortex - massive infarct would be needed to completely wipe it out
• area of the visual cortex that involves the macular vision has 2 diff blood supplies - both would need to be blocked

Question 24

if there is superior visual field loss, what optic radiations are affected?

Answer 24

optic radiations in Meyer’s loop

Question 25

if there is inferior visual field loss, what optic radiations are affected?

Answer 25

optic radiations in parietal lobe

Question 26

what does the acronym "PITS" refer to in homonymous quadrantanopia?

Answer 26

Parietal lesions cause an Inferior defect Temporal lesions cause a Superior defect