Cornea, iris and pupil

The cornea is a clear layer at the front of the eye which is continuous with the sclera, as you can see in Figure 5.2. You can also see that the cornea is located in front of the iris. The main purpose of the cornea is to help focus light as it enters the eye. The iris is the coloured part of your eye and is made of muscle. The iris controls the amount of light that enters the eye through the pupil. The central opening in the ring-shaped muscular tissue of the iris is called the pupil, and the amount of light that enters the eye, can be altered by the iris changing its shape.