Eyes

 

How do my eyes work?

                         Your eyes are tough balls of tissue that contain dear jelly. They work by producing an image that is transmitted to your brain as ‘sight’. A transparent layer, called the cornea, covers the front of each eye. Below this is the iris, which is a flattened ring of muscle surrounding the pupil.

                       Light enters the eyeball through the pupil and passes to the lens behind. As the light rays pass through the lens they are bent and focused to form a clear image on the retina. The retina detects this image and turns it into nerve impulses. These impulses travel along the optic nerve to the brain. The brain interprets them as a picture that you can see.

 

 

What makes our eyes coloured?

                                  Eye colouring is caused by melanin in the iris. This is the same substance that your skin produces when you tan in the Sun. Eyes can be various shades of brown, blue, grey or green, depending on how much melanin they contain. Brown eyes have much more melanin than blue eyes. You inherit your eye colour from your parents. The colour of the iris is very individual, and it has been suggested that it could be used to identify people in the same way as fingerprints.

 

 

Why do I blink?

                    Blinking cleans and lubricates the surface of the eye. The cornea is very sensitive and must be protected from infection and from drying out. Every time you blink, which is normally every few seconds, a film of tears washes the eye’s surface clean. It wipes away bacteria and dust, and leaves behind a moist, lubricating layer that also contains substances to kill bacteria.

                  Blinking is a protective reflex of the body. You can over-rule it for a time and try to stop yourself blinking, but very soon your brain will decide that blinking is essential and you will not be able to stop it from happening. The flow of tears increases when your eyes are irritated, or if a draught causes the surface of the eye to become dry. Excess tears drain away through a duct in the corner of the eye, and pass into the nose.

Pictures Credit: Google