The human body is the product of natural laws. If natural laws are violated the body will suffer…same is true with the eyes.
Namely, natural refractive state of the eye is a farsightedness (hyperopia). It means that the eyeball is short and light rays which coming from eternity are focused behind the retina. With this refractive state people are born with very few exceptions.
However, human eye is provided with mechanism which enables us with possibility of seeing clearly both at far and close distances. This mechanism is called accommodation and it is performed by the focusing muscle of the eye (ciliary muscle). This mechanism gradually decreases through the life and around 45 becomes too low to see objects clearly which are close to the eyes and plus glasses become necessary for the close work. This condition is named presbyopia.
While we are young the body develops and also the eyes. It means that short farsighted eye becomes elongated in order to achieve ideal refractive state of the eye (emmetropia) and this process of development of the eye is named emmetropization.
However, in modern society accommodative stimuli is so increased due to the close work that the development of the eye does not halt at zero point (state of emmetropia) but exceeds it and the eyes become so elongated so much that they go to the minus side and thus become nearsighted (myopia).
In this way myopization is nothing other than emmetropization which exceeds the zero point, i.e. the state of emmetropia to the minus side. In other words overelongated eye.