Is there a reason for visual changes tha occur fast?

Dry eye. Your description sounds like dry eye. Initial treatment is frequent artificial tears during the day, ointment at night, warm compresses a few times a day, and omega-3 fatty acid supplements. If no improvement, you should see an eye doctor for further evaluation.
Yes depends. Yes but it depends on the changes. Severe changes should be evaluated immediateley while mild changes may be related to dry eye that can be seen after lasik. If this is something that is occurring i would see your eye doctor.