Visual Pathways Flashcards
what si the basic structure of the eye
3 layers
- sclera/cornea
- choroid/ciliary body/iris
- retina
what is sclera
tough CT
what is cornea
sp anteriorly of sclera
what si the choroid
middle coat major vasculature and sp anteriorly
what are the specialisations of the choroid anteriorly
ciliary body nd iris
is the optic nerve middle
no more near nasal side
what does lens essential do
focus
sparical nature turns things upside down ned backwards
who does lens become round
by reducing tension in it
what is the optic nerve myelinated by
oligodendrocytes
what si the iris
light regulator
what does the sclera and cornea like
sclera - white
cornea - transparent
what is function choroid
absorbs light - prevents rfelcton
what does ciliary body do
produces aq humour
what does retina contains
photoreceptors - rods and cones
where is blind spot
just lateral of visual field
where is visual axis
in midline back to fovea
what is fovea
place of highest acuity of vision
what are th two fluid filled cavities of the eye
aq humour and vitreous humour
what is the flow of humour aq
choroid form ciliary body which secret aq humour behind iris flow to ant chamber
where is aq humour reabs
by canal o schlemm
what happens if canal of scheme block
build pressure in ant chamber which pressure on lens and pressure retina - blindness - glaucoma
what are suspensory ligament
fibres radiate form lens to change shape
what are the two types of receptors
rods and cones
what are rods sensitive to
in dark and light situation
black and white
very esnitve
what are cones sensitive to
red
blue
green
less sensitive
what happens to cells in repose to light
hyperpolarises
what do ganglion cels do
respond to contrast/ movement, colour/detail
what si the topic here fibres form
ganglion cells
what cells changes ganglion cell function
amacrine and horizontal cells
does the optic disc have receptors
no
what si the optic disc used to look at
at CNS coated by dura/arachnoid
what is fovea centralise
point of fixation
what happens to optic disc in papillooedema
clear edge becomes blurred of optic disc
what is the vision like at fovea centralis
detailed high resolution colour vision
point fixation thinning of retinal layer
what are the reason for high visual acuity
thing of retinal layers
lack of rods high conc of cones
low convergence
what causes a blind spot at optic disc
lack of rods and cones
what are the elements of visual athway
optic nerve optic chiasm optic tract lateral geniculate body - thalamus optic radiation strate cortex - primary visual cortex
what is the term the axons do to get to straits cortex
radiate
trace the pathway of the right visual field
imaged on left retina temporal fibres don't cross nasal fibres cross at chiasm right field rep in left optic tract relay process in LGN project to left primary visual cortex
what is meyers loop
part of the optic radiation, sweeps back on itself into temporal lobe, just lateral to the temporal horn of the lateral ventricle.
what happens when negotiating lat ventricle into banks
of calcimine sulcus
what happens to sight inv macula when stroke
sustain enough blood for sparing vision but loss of peripheral vision
what si visual processing
info in retina - colour, orientation, form
segregated in pathway and cortex
what blood supply is to visual processing visual cortex
lately post cerebral
what is blood supply which lead to macular sparing i stroke
post/middle cerebral arteries overlap at occipital lobe
what is monocular vision
meaning curtain coming down altitudinal loss of vision (in one eye or two if binocular) ut optic nerve behind eye
what is bitemporal hemaniopia
blindness coz outer half of both the right and left - cut at chiasm
what is Homonymous hemianopia
loss of half of the field of view on the same side in both eyes cut further back form chasm one side
what is Upper quandrantanopia
loss of vision in the same lower or upper quadrant cut during radiation to cortex
what is the pupillary reflex
when light shine in eye pupil contract bilateral
what happens in pupillary reflex
light in to pretectal region
oculomotor nuclei
ciliary ganglion
contract pupil
what is accommodation rfele
when look to distance to something close
what does accommodation produce
lens thickening - ciliary muscle
pupillary constriction - increase field depth
convergence of eyes - medial recti
what is ‘normal vision’
able to focus both distant and near objects
what is myopia
short sighted
able to focus near
unable to focus far
eye ball too long
treat - concave lens to diverge light
what is hyperopia
long sighted
unable to focus near objects
able to focus distant objects
eye ball relatively too short
treat - convex lens to converge light
what is presbyopia
normal age change
gradual loss accommodation
lens less elastic
ciliary muscle weaker
treat - convex lens t converge light
what are saccades
jumps from opposite frontal eye fieldncannot do smoothly
what are pursuit movements
smooth move to sep objects fixed on fovea
in assc cortex same side
