It could be just eyestrain
. But nevertheless you must consult an ophthalmologist. If it turns out to be something organic, you may be referred further to a neurologist
If you are on the computer for long periods, it is better you follow the 20-20-20 rule..... every 20 minutes, look away at an object that is at least 20 feet away for at least 20 seconds. And make sure the monitor height is just below your horizontal eye level.