Your eyes allow you to see the shapes and colours of the world around you. They are sometimes described as your windows to the world.
Parts of the eye
Your eye is a globe about 2.5 cm across. It is not perfectly round.
If you look at one eye in the mirror, you can see:
- the iris, which is the coloured part
- the cornea, which is the clear dome over the iris
- the pupil, which is the black hole in the centre of the iris
- the sclera, which is the white part
- the conjunctiva, which is a thin layer of tissue covering the front of your eye, except the cornea.
Others parts you can’t see are:
- the lens, which sits behind the pupil
- the retina, which is the inside of the back of the eye
- the optic nerve, which is at the back of the eye.
How the eye works
The eye converts light into electrical signals that your brain converts into sight.
Light enters your eye through your cornea, then continues through the pupil and lens.
The cornea and lens focus the light onto the retina.
The retina is a layer of nerve tissue that includes:
- rods, which identify shapes and movement
- cones, which detect detail and colours.
Rods and cells absorb light signals, change them into nerve impulses, and send them to your brain via the optic nerve.
Your brain recognises the nerve impulses as a visual image.
Causes of vision loss
Blindness and poor vision can be caused by:
- disease and infections,
- exposure to light or chemicals
Some people have vision impairment when they’re born, or soon after birth.
Some eye conditions can cause damage to your vision. You should see a doctor or optometrist if you’re worried about changes in your vision.
For many people with blurry vision, glasses or contact lenses will help.
Read more about eye conditions.
Tips for healthy eyes
To keep your eyes healthy:
- have your eyes checked every two years
- protect your eyes from sunlight – wear a hat and sunglasses with UV protection
- eat healthily – green leafy vegetables, fish, linseeds, and some vitamins and minerals can help prevent macular degeneration
- protect your eyes from injury at home and work
- avoid smoking.
If you have children, have their eyes checked regularly, especially if they say they can’t see clearly.
Read more about eye care.
Last reviewed: August 2015