How long should a person sit in front of a computer screen?

If you work long hours on the computer then it is advisable that you take breaks regularly. Spending too much time in front of the computer screen is not only bad for your eyesight but it can have a toll on your body too. It's common to find most people spending long hours at their computer without realizing the hazards it can cause. It's important that regular breaks will help relieve any tension that may have built up in the mind and body. Leave your workplace every fifteen or thirty minutes and take a short walk. This will provide your eyes the rest it requires before you head to the screen once again.

There is no certain limit to a user but for long hours, a person should take timely breaks and relax eyes. You can try blinking, warm palm method, looking at distant object (might be from outside window), wash eyes with tap water etc