Why not take a break when you feel tired? I think the best way to reduce eye strain is to buy a pair of prescription glasses if you have any vision problems, because glasses can help your eyes see clearly so you won't need to squeeze your eyes and this will reduce eye strain. Besides, have a rest during your work is very important for your eyes. The eye muscles will strained if you work for a long time, so you need to do some exercise or see the things in the distance for a few minutes to relax them. You will find that this kind of activity can refresh your mind as well as reduce eye strain. Good luck!