What makes your eyes weak....?

I believe that the computers and television can affect one's eyesight . Constant staring at a screen is hard on the eyes because of the constant flickering . If you have ever noticed that when you have a headache how hard it is to watch television or to be on the computer , it would be pretty much the same thing . This will make your eyes more sore if you already have a headache so think what the constant use of this will do over time . This would be my guess anyway . I know my mother in law has developed bad eyes just since she got her computer and she would be on it a lot as she doesn't do much of anything else . She was told this was due to using the computer all the time .