The eyes are designed for a healthy balance of looking both in the near and far fields of vision. This design served us well when hunting and farming were our way of life. With the advent of computers, books, living and working indoors, and other changes in our lifestyle, the average person now spends the majority of their day looking in the near field of vision. When you look in the near field of vision, the ciliary muscles around the lens contract to make the lens convex. Conversely, when you look away at something far at a distance, the ciliary muscles relax, and there is a flattening of the lens that requires no effort. It becomes a wonderful exercise for the visual system, because when you look far at a distance, the total eyeball itself becomes a bit shorter than when you are looking at your near field of vision.
In this way, to look far at a distance is the most natural and relaxing exercise that your eye can have. In addition, there is actually no mental activity involved, so you can mentally relax as well, and simply enjoy whatever the eye sees.
When sitting in front of the computer, try to do this exercise every ten minutes for fifteen to thirty seconds. It takes less than a minute, and is a wonderful rest for your eyes.