Another cause of computer eye strain is focusing fatigue. To reduce the risk of tiring your eyes by constantly focusing on your screen, look away from your computer at least every 20 minutes and gaze at a distant object (at least 20 feet away) for at least 20 seconds. Some eye doctors call this the 20-20-20 rule. Another exercise is to look far away at an object for 10-15 seconds, then gaze at something up close for 10-15 seconds. Then look back at the distant object. Do this 10 times to avoid your eyes ‘locking up’ (a condition called accommodative spasm) after prolonged computer work.