Variable . Computer eye strain is very common complaint now a days. Also called video or terminal display syndrome results from prolong focus on an electronic display. Usually symptoms of dryness, burning, stinging, fatigue , and blurriness are present. Take frequent breaks, and look away at distant objects. Use artificial tears. Close your eyes for a few minutes are a few suggestions.
It varies. True eye strain is a result of either dry eyes from staring too long at the computer, or an uncorrected refractive error (nearsightedness, farsightedness or astigmatism). If it is caused by dry eyes, it can be relieved within minutes by using artificial tears and taking a break from the computer. If due to a need for glasses, it will return soon after getting back to the computer.
Variable. It varies from person to person. Take break and use some artificial tears. If it persists, try taking a nap.
Computer. About 20 minutes or so. Try some cold artificial tears, such as theratears. Look at something far away out the window to relax your focus. Close your eyes for 5 minutes. Soon, you will feel normal again. Try to take frequent breaks during computer use and keep using artificial tears...