Nature intended eyesight to be set for distance, since this was the most important attribute during most of mankind’s evolution, and so children develop their distance vision first. Today, we have far too many things that are colourful and near and, also, children are encouraged to start their education earlier and earlier thus spending less and less time outdoors. In fact, some parents keep their children indoors (mostly using their near vision) much more than outdoors (developing distance vision).
From the above we know that the growth of children's eyes is influenced by what the child sees or the environment in which the child lives. Problems arise because of extensive near activities such as reading, playing video games and doing school work. Even watching TV locks the eye-focusing system into the distance to the TV.
Let's try an experiment to illustrate how the eye-focusing system, which is operated by all the muscles in and around the eye, works.
Make a fist and cover with the other hand, hold tight for 3 secs.
Make either the left or right hand into a fist. Then, with the other hand squeeze it really hard for a few seconds.
Remove the hand and try to move your fingers. Is this easier or is it more difficult?
It's more difficult, right?
This is how the eye muscles feel when you hold your focus at one distance for a long time. Medically this is known as sustained accommodation. The eyes are not designed to look at a book or an iPad for hours, days, weeks, months, or even years but the eye-focusing system adapts to the environment in which it finds itself.
The result is the onset of myopia or near-sightedness.
The child is then fitted with glasses in order to correct the refractive error.