the eye Flashcards
what does the conjuctiva do?
lubricates and protects the surface of the eye
what does the sclera do?
it protects the eye - it is the tough outer layer
what does the cornea do?
it refracts light into the eye - it is transparent. It has no blood vessels, so oxygen diffuses from the outer surface
which part of the eye controls how much light enters it?
the iris - think goddess of the rainbow because rainbows are created through light
what does the iris do?
its diameter increases or decreases to control how much light can enter the eye
what does the lens do?
it helps to focus the light on the RETINA so you can see objects close and far away
what does the optic nerve do?
It carries impulses from the receptors to the brain
Why is the iris reflex important?
very bright light can damage the retinas eg the sun so more light causes the iris to get smaller and less causes it to get bigger
—> objects can be seen in different lights but it won’t harm the eye
What are rods in the eye? Where are they?
- In the retina
- it is a light receptor that works best in dim light
- can’t sense colour
What are cones in the eye? Where are they?
- In the retina (fovea)
- are light receptors
- see colour well
- can’t see dim light
if someone is short-sighted, this means…
they can’t see distant objects
If someone is longsighted, this means…
they can’t see close objects
If someone cannot see near objects/is longsighted, their eye is
- cornea/lens doesn’t bend the light enough
- the eyeball is too short
If someone cannot see far objects/is shortsighted, their eye is
- cornea or lens bends the light too much
- their eyeball is too long
in order to look at distant objects or close objects, which muscles contract?
ciliary muscles
