Topic 5.4- 5.2: The Eye Flashcards
What is the first structure light meets when it hits the eye and what does it do
the cornea- transparent and concave so the light refracts and focuses on the pupil
What is the iris
the coloured bit of the eye and controls how big or small th pupil is
What is the lens
A concave lens that can change shape in order to refract the light on the retina at the back of the eye
What are the two different types of receptor cells on the retina (and whats the difference)
cones -allow us to see in colour
rods- allows us to see more light but in black and white
What is the optic nerve
a nerve that takes all the impulses from the retina to the brain
what happens to the iris in bright light
it constricts and the pupil becomes smaller
what happens to the iris in low light
it dilates and the pupil becomes bigger
What are the two muscles in the eye
circular muscles
radial muscles
what happens to the msucles in the iris in order for it to constrict
the cicrluar muscles contract
the radial muscles relax
what happens to the msucles in the iris in order for it to dilate
the circular muscles relax
the radial muscles contract
What is the area with high concentration of cones where light focuses
fovea
what is the scelera
tough layer round the outside of the eye
Define accomadation
a reflex that controls the shape of the lens
what controls the shape of the lens
the cilliary muscles and the suspensory ligaments
what happens when the eye focuses on something near
- the ciliary muscles contract
- which means there is slack in the supensory ligaments
- which gives slack to the lens making it fatter and more curved
- which will refract the light more
what happens when the eye focuses on something far
- the ciliary muscles relax
- which means the supensory ligaments tighten
- which pulls on the lens making it thinner
- which will refract the light less
What is hyperopia
long sightedness
- cant focus on objects close by meaning light focuses behind retina
- eyeball is to short
- lose elasticity in lens refracts to little
What is myopia
short sightedness
- cant focus on things far away
- eyeball is to long
- the lens is to thick and refracts to much
How do you correct hyperopia
with a convex lens which makes the light refact more
How do you correct myopia
with concave lens to make the light diverge before refracting
what are other methods of correcting eye defects (not glasses)
- laser eye surgery to reshape the eye
- replacement lens
