Concept:Iris is a dark muscular diaphragm that controls the size of the pupil. The pupil is a small opening that regulates the amount of light entering the eye.Explanation:The iris contracts and relaxes to change the pupil size. In bright light, it narrows the pupil to reduce light entry. In dim light, it expands the pupil to let in more light. This automatic adjustment protects the retina and improves vision. Other parts of the eye have different roles as shown below.
Cornea
The front part of the sclera is called the cornea.Light enters the eye through the cornea.
Retina
It contains highly specialized nerve cells.These convert the light which is focused there into electrical signals.These are then passed through the optic nerves to the parts of the brain which process vision and build up the picture that we see.It is a light-sensitive layer that consists of numerous nerve cells.It converts images formed by the lens into electrical impulses.
Lens
Behind the pupil, there is a structure called a lens.By the action of ciliary muscles, it changes its shape to focus light on the retina.It becomes thinner to focus on distant objects and becomes thicker to focus on nearby objects.
