The eye Flashcards
what does the cornea do
it starts focussing the light rays
what does the iris do
Coloured part, which controls the size of the pupils
what do lens do
focus light rays onto the back of the eye
- can change shape allowing us to focus on distant or near objects
what does the retina do
contains the light receptors, allows us to detect light intensity and colour
what does the optic nerve do
carries impulses between the eye and brain
what does the sclera do
white part of the eye that protects the eye
what do sensory ligaments and ciliary muscles do
allow us to focus on distant and near objects
what happens to pupils in dim light
1 - radical muscles of iris CONTRACT
2 - circular muscle of iris RELAXED
3- pupil becomes more dilated, so more light enters the eye
what happens to pupils in bright light
- radical muscles of iris RELAX
- circular muscles of iris CONTRACT
- pupil contracts, so less light enters the eye and protects it from damage
what is accomodation
the process of changing the shape of the lens to focus on near or distant objects.
what happens when our eye focuses on a near object
- the ciliary muscle muscle contracts, the suspensory ligaments loosen, making the lens thicker and able to refract light rays more strongly
- light rays also focused on a point on the retina
what happens when our eye focuses on a distant object
- the ciliary muscle relaxes
- suspensory ligaments are pulled tight
- lens pull thin and only slightly refract light rays
- light rays are now focused to a point on the retina
what causes short sightedness and what happens when someone has it
- eyeball being too long, so light is focused at a point infront of the retina
- or lens being the wrong shape (too thick)
- they can only see things close up
how to treat short sightedness
treated using concave lens which partially unfocus light before it enters the eye
what causes long sightedness and what happens when someone has it
- eyeball is too short so light is focused at a point BEHIND the retina
- so they can only see things from far away clearly
- a loss of elasticity in the lens - meaning it cannot become thick enough to focus
how to treat long- sightedness
treated using convex lens which partially focus the ight before it enters the eye
biology word for long sightedness
hyperopia
biology word for short sightedness
myopia
what does laser surgery do
changes the shape of the cornea so that it refracts light to a greater or lesser extent
how do contact lenses work
They float on the surface of the cornea. They work like glassses,by focusing and refracting the light.
how do replacement lens work
implanting artificial lens, and placing them in front of original lens through a small cut in the cornea
to focus on near objects, the lens become
thicker
to focus on distant objects, the lens become
thinner
what is the eye and what does it do
a sense organ which contains receptors sensitive to light intensity and colour
what is the pupil
- the space in the centre of the iris which light passes through
what does the ciliary muscle do
changes the thickness of the lens
