[header] How to tell when you are straining your eyes [title] Check for sore, tired, burning or itching eyes. [step] If your eyes start to itch, burn or get tired, this might be a symptom of eye strain. Keeping your eyes focused for long periods of time at the same distance can sometimes cause eye fatigue. 
If this happens, take a break from what you're doing. A damp washcloth laid over the eyes may help relieve the discomfort.