Relax eyes by rolling them. Turn your head up and down, right and left, and meanwhile roll your eyes to the same direction your head turns to. Remeber that when you turn you eyes to a direction, make them see the very corner of that direction.
Relax your eyes by blinking. This method is extremely easy because we can do it anytime and anywhere. Whenever you feel that your eyes need rest, just turn your face upward and blink. It does not only relax your eyes but also your neck!
Relax your eyes by looking far away. This needs you to pick a good position where you can look as far as possible. After looking far a about 3 minutes, draw your eyes back and turn them on your own palms for about two minutes. You can repeat this several times during your work break.
Relax your eyes through massage. You do not need a professional to do this as massage mentioned here simply refers to drawing circles around your eye sockets. The effects will be better if you get your hands warm first, then draw a circle around both eyes in clockwise direction first and then in anticlockwise direction. Repeat it for several times.