The Eye Flashcards
what is the function of the retinal pigmented epithelium
contains melanin to ensure theres not excessive light refraction
anchors the photoreceptor cells in the neural layer
what are the 3 types of photoreceptor cells in the neural layer of the retina
rods
cones
horizontal cells
what do rods do
responsible for black and white vision
what do cones do
responsible for coloured vision and high definition
what do horizontal cells do
responsible for lateral inhibition
what are the layers of the retina
Pigmented layer and Neural layer
what region of the retina contains no photoreceptor cells
the blind spot where the optic nerve leaves
what is the macula responsible for
central vision and acuity
what type of photoreceptor is abundant in the macula
cones
what artery supplies the retina
central retinal artery
what will happen to the optic disc in raised inter cranial pressure
it will swell
describe the light reflex
light stimulates the afferent CN II
nerve synapses with both Edinger Westphal Nuclei
efferent CN III gives a parasympathetic response causing direct and consensual pupil contraction via constrictor papillae
in what area are the edinger westphal nuclei found
pretectal area
describe the accommodation reflex
light stimulates the afferent CN II
nerve synapses at the lateral geniculate nucleus and goes to the primary visual cortex in the occipital lobe
efferent CN III causes convergence of pupils, pupil constriction and ciliary muscle contraction to give a more convex lens
describe the root of the optic tracts
they go to the lateral geniculate nucleus in the thalamus where they then spilt into radiations
describe the visual pathway
optic nerve - made up of 4 fibres from the ipsilateral eye
optic chiasm
optic tracts
radiations
where do the radiations travel to
the primary visual cortex in the occipital lobe
what happens to the fibres at the optic chiasm
the nasal fibres decussate
the temporal fibres remain ipsilateral
what visual field are the nasal fibres responsible for
temporal visual field
what visual field are the temporal fibres responsible for
nasal visual field
what visual field are the superior fibres responsible fore
inferior visual field
what visual field are the inferior fibres responsible for
superior visual field
what type of visual loss occurs due to optic nerve damage
monocular blindness - cant see from the ipsilateral eye
what are the causes to optic nerve defects
retinoblastoma, meningioma
what type of visual loss occurs due to optic chiasm damage
bitemporal hemianopia
what fibres are affected in optic chiasm damage
nasal fibres
what causes optic chiasm damage
pituitary gland tumour
what type of visual loss occurs due to optic tract damage
left/right homonymous hemianopia
what are the causes to optic tract defects
neoplasia and trauma
what type of visual loss occurs in radiation damage
quadrantanopia
what is macular sparing
where the macula is not damaged when the occipital lobe loses its blood supply from the posterior cerebral artery as the macula is still supplied by the middle cerebral artery so you still have central vision
