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.
Benign eye floaters are tiny floating specks or cobwebs in your vision. Cataracts A cataract is a cloudy area in the lens of the eye and can cause blurry or dim vision. Diabetes, type 2. Diabetes can make you feel hungry, tired, or thirsty; you may urinate more than normal and have blurry vision. Macular degeneration. Macular degeneration is a painless eye condition that causes you to lose your central vision.