Relax your eye muscles by shutting your eyes and relaxing for a little time
Roll or blink your eyes, close them tightly for a few seconds.
Change your focus every 15-30 minutes. Look in another direction, or across the street, or change from looking at the computer and getting up for a drink.
Try an over the counter teardrop product to soothe your eyes if they feel dry after reading, knitting or staring at the computer for a particularly long time.[1]