week 7: the eye Flashcards
features of Anterior Chamber
located between cornea and iris
Has aqueous humour fluid:
- maintains spherical shape
- drains into canals of schlemm (insufficient drainage leads to glaucoma
features of vitreous body
large sphere filled with vitreous humour fluid gives spherical shape
features of the outer layer of vitreous body
outermost layer: sclera
- white of eyeball
inner layer: choroid
- has ligaments which control shape of lens
- contains blood vessels for nourishment
features of Iris
has two sets of smooth muscle controlled by oculomotor nerve which regulate the pupil size
1) inner muscle
- circular
- contricts/closes inner iris
2) Outer muscle
- perpendicular to circular muscle
- opens the inner iris
features of lens
- Held in place by the ligaments from choroid
close objects: curved shape
far objects: flattened shape
once light rays pass through lens they are refracted onto retina/fovea
what is focal point and focal length
how does focal length change
focal spot: area of retina where light is focused on by lens
focal length: length from lens to focal spot
- focal length will be long when lens is flat (i.e far object)
- focal length will be short when lens is curved
(i. e close object)
what are the 3 main ways light is refracted before reaching the retina
- Air to cornea (greatest amount of refraction
- cornea to aqueous humour
- lens to vitreous humour (greatest amount of focus occurs)
what are the three main ways the eye ACCOMMODATES for near and far objects
1) contractions of cillary muscles in choroid
- lens bulging/ flattening (curved is close)
2) contractions of pupils
dilation/constriction
3) convergence of eyeball
- focuses light onto fovea
what is the fovea
area on retina where greatest visual acuity occurs
features of the retina
has two main photoreceptor: rods and cones
rods mainily located on peripheral.
cones located centrally in fovea
What are rods and cones
Rods
- 120 mill
- used for black/white visualisation
- can be stimulated by less intensity then cones
Cones
- 60 mill
- colour
- less sensitive/ i.e better for small details.
- have red(large) green(medium) and blue (small) cones
what is blind spot
on the retina where the optic nerve exits there is no photoreceptor present. therefor if light was focused nothing will be received. i.e can’t see.
what happens to rhodopsin during light and dark adaptation
light:
rhodopsin broken into retinal and opsin
dark:
retinal and opsin built into rhodopsin.
