Describe how does human eye work?

The following steps are involved in the functioning of the eye. 

1. A light ray which is incident on the object is reflected back and it enters our eyes through cornea. Cornea is called window to the world. Cornea is transparent.
2. Behind the cornea, there is a dark muscular structure called Iris. Iris is that part of the eye which gives eyes it's distinctive color.
3. In the iris, there is a small opening called the pupil. Size of the pupil is controlled by iris.
4. Behind the pupil of the eye is a lens which is thicker at the centre. Lens focuses the image of the object on the retina.
5. Retina converts these optical images into optical pulses. These optical pulses are then sent to brain through optical nerves.
6. The amount of light entering the eye through cornea is controlled by Iris. It expands when light is bright and thus enables controlled amount of light to enter the pupil. In dark it contracts and increases the size of pupil to allow more light to enter the eye.