Diagram of eye

Eyes are the sense organs which give us the sense of vision. The human eye is almost spherical in shape. Following are the main structures in the human eye.

Cornea: The eyeball is covered with a tough layer. This layer is transparent on the front. This transparent portion is called cornea.

Iris: Iris is a thin circular structure. It works like the shutter of a camera. It controls the amount of light entering the eye. The colour of iris imparts distinct colour to the eyes of an individual. A person with blue iris has blue eyes.

Pupil: There is a hole in the centre of iris. This is called pupil. Light enters the eye through the pupil. When the light is bright, iris contracts and thus allows less light into the eye. When the light is dim, iris dilates and thus allows more light into the eye.

Lens: Lens is present behind the pupil. The lens in the human eye is a convex lens. The size and thickness of the lens change as per the distance of an object.