The "20-20-20" Rule
To help you deal with this problem, the 20-20-20 rule suggest that after every 20 minutes, you (the computer user) should take a break for at least 20 seconds and look at objects that are 20 feet away from you. This gives yours eyes a break and chance to adjust focus-a great way to avoid visual fatigue.
***One good idea is just simply to follow the 20 20 20 rule.
Peace Out! :D