When this happens, the eye cannot focus properly and the eye becomes worse.
This is believed to be caused by heredity. In other words, parents with poor eyesight often produce children with poor eyesight. Conversely, parents with good eyesight tend to produce children with good eyesight.
Another cause is that the lens in the eye does not work properly.
The lens is like the lens in a camera, and its function is to change thickness to adjust the focus. When looking at objects in the distance, the lens is a thin lens, but when looking at objects up close, the lens is a thick lens.
However, if you look only at near objects all the time, the lens remains a thick lens and may not completely return to its original state. When this happens, you can see near but not far, and the distance becomes blurred and unclear.
Staring at the near for a long time is quite common in daily life. For example, reading a book in a bad posture. Studying. Watching TV. Playing video games. These are all things that involve staring at the object for a long period of time. However, it is not necessarily true that doing the things just mentioned will always cause eye problems. There are people who are avid students and people who play video games all the time who also have good eyesight. In other words, these things can trigger eye problems, but they are not the only things that can cause eye problems.
The important thing is not to overdo anything. If you divide your time between playing video games and playing outside, or watching a little TV and then studying, it is unlikely that your eyes will get worse just because you play video games or watch TV for a little while.