Many people like to spend too much time on their smart phone, when their eyes focus on smart phone for a long time, actually it will harm their eyes. "When your eyes focus on the small images and text you see on the small screens of smart phones. Over time, this has been found to lead to problems with focus and vision, especially if you already use vision correction, like glasses or lenses." (weavereye.com) When people have watched small screen in long time, the eyes have a rough time correcting for distance. When your eyes work too hard, it usually results in unpleasant headaches as a result of the eyestrain. In addition to this, too much time looking at your small screen can reduce your blink rate, and that can lead to dry eyes and blurry vision. So play smart phones in long time that will seriously damage the eyes health.