Eyestrain always happens when your eyes get tired from excessive or intense use. It is vexing. However, it will disappeared with enough rest. Moreover, eyestrain usually begin to appear after extended computer use, reading, straining your eyes in dim lighting, or during activities that involve prolonged visual tasks. Although it's not often a serious condition, eye strain could be a symptom of an underlying problem. Eye strain is known to cause fatigue, difficulty concentrating, and headaches.