I'm not so certain that the issue is the definition of the term normal, so much as it is the value (positive or negative) or association (healthy vs. unhealthy) the term implies in a medical or social context.
One of the most common reasons for blurry vision while wearing contacts is that your eyes are dry. Some people have a medical condition that causes dry eyes, called dry eye syndrome, but others' eyes are irritated by the contacts themselves.
4. Effects of Wearing Contact Lenses. If you wear contact lenses, this may well be the reason why you experience pain when blinking your eye. The lens can irritate your eye and even limit the oxygen supply to the cornea. This usually happens when you over-wear the lenses.