Here is an exercise I learned during a course in eye-care. It's been such a long time since then I don't know if I've added or subtracted anything, but I think I can say that it is essentially/basically what I learned. It is easy to do and can be done safely by all with little or no fear of over-exertion etc. Standing, with legs about shoulder-width apart swing your shoulders in one direction letting your arms naturally follow the swing and shifting your weight to the leg on that same side. Then swing in the opposite direction. Try not to move your feet around; keep them in same place. While doing the exercise, as your turn/twist your body, focus your eyes far off into the distance as if you were viewing far off mountain ridges. Let your eyes run over these "ridges" as if you had a long pole extending from your eyes all the way into the distance and that there is a brush at the end of the pole and you are brushing the mountaintops. When you get things right you will find that your eyes will naturally flick back and forth during the exercise. Try to see all movement originating from the small of your back. Let your arms hang freely; don't make them swing but let them swing naturally with the movement at the small of your back that turns your shoulders which turns your arms.I find this exercise helpful after a long session at the computer or when I don't feel inclined to do other exercises.