By Elise 8F
How it works
A tough white layer called the sclera, covers the outer part of the eye. In the area that protects the eyelids, close to the front of the eye, a transparent membrane called the conjunctiva covers the sclera, which runs to the edge of the cornea. The clear curved layer in front of the iris and the pupil called the cornea, is where the light enters. The cornea also helps focus light at the retina and is a protective covering to the front of the eye. Light travels through the pupil once passing through the cornea. The iris is what controls how much light comes into the eye. More light is allowed inside of it when the environment is dark, but when the environment is bright less light is allowed in. The pupil shrinks and enlarges like the aperture of a camera, depending on the amount of light around it. It's size is controlled by pupillary sphincter muscle and dilator muscle.