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How do your eyes work?

Image of an eye. There is text surrounding the image. Going clockwise from the top left corner it says: iris, upper eyelid, sclera, lower eyelid, caruncle, pupil.

Your eyes are like a camera, they have a lens at the front that allows light through and clever machinery at the back. But how do they work? Look into each other’s eyes, what do you see? Different colours? This is the iris of your eye. Do you see the black pupil in the middle? This is what allows light into the eye. Have a look at what happens to the iris when you go from a dark room to the sunshine outside. Did you notice anything happen? When it’s sunny the iris becomes small and lets less light through but when it’s dark the iris gets bigger and lets a lot of light through. Actually, this light first passes through the cornea, then the iris and then the lens until it reaches the retina at the back of the eye. The retina is made up of lots of cells that react to light. The cells create signals when light hits them and they pass these signals onto the optic nerve. It’s the optic nerve’s job to pass these signals to the brain and the brain can figure out what they mean and explain what you’re seeing.
 

Diagram showing the cross-section of an eye. Text runs along the left and right hand side of the image saying ' Sclera, Cornea, Pupil, Iris, Lens, Ciliary Muscles, Vitreous, Retina (cones and rods), Optic Nerve.