Strain can be caused from things such as
- squinting
- concentrating too long
- reading in low lit conditions
- sitting at a computer all day
What Do You Do?
So the main question is what can you do to prevent this from happening and unfortunately you really can't but there are methods that you can go through that are very beneficial to reducing the strain and therefore helping you see more clearer.
The method I am talking about is called relaxation and is a great way to improve eyesight naturally.