Explain the structure and functioning of Human eye. How are we able to see nearby as well as distant objects?

The structure of human eye is as follows:

Function of human eye:

The human eye acts as a camera. The lens system of eye forms image on Retina which is a light sensitive screen. Light is entered through a thin membrane known as cornea. It forms the transparent bulge on the front surface of eye ball. The eye ball is of diameter 2.3 cm. The maximum refraction of light is refracted at the outer surface of cornea of eye. The crystalline lens provides adjustment of focal length which is required to focus different images on the retina. Iris is a dark muscular diaphragm which controls the size of the pupil. Light entering the eye is controlled by the iris. An inverted, real image is formed by lens on retina. Retina is a delicate membrane which consists of number of light sensitive cells. Upon illumination, the light sensitive cells get activated and electrical signals are generated. These signals are then sent to brain through optic nerves. The signals are interpreted by the brain and the information is processed and we can see the objects.