How do our eyes work?
Light enters a small opening in the center
of your eyes, called the pupil. Pupil is covered by clear protective shield.
The muscles in the coloured iris around the pupil change its size and control
the amount of light that enters eye. Then the light passes through a lens, which
focuses an image on the retina at the back of the eye. The retina contains that
sends messages to the brain through the optic nerve. Actually, the image (of
what we see) on the retina is upside down, and our brain turns this image the
right way up. Sometimes our eye can be compared to a modern video camera. In
camera, focusing involve moving lens in and out. But the eye uses the natural elasticity
of its lens to alter its shape (the focal length). This action, which is completely
automatic, involves the contraction of a ring of muscles against the pressure
of fluids inside the eye.