Why does vision blur?

Many possibilities. Blurred vision can be cause from many different reasons. A need for glasses is probably the most common cause for blurred vision but it can also be caused by dry eye, cataracts, retinal damage, or many other causes. If your vision is blurry see your ophthalmologist for further evaluation.
Different reasons. Blurry vision is a fairly common complaints and may have several causes, some of them may not necessarily be eye related such as pre-syncope (near fainting). Keeping eyes closed for a while (like after a night sleep) may cause "normal" blurriness or changing gaze from a distant object to a near one rapidly, may cause blurry vision. I would recommend obtaining professional advice, though.

Related Questions

Why does my vision blurs when I stand up and start walking?

Please seek eval. This is not a typical symptom. You should see an eye doctor. This may represent poor blood flow to your eye. You are very young to have significant orthostatic hypotension (low blood pressure with changes of position). If female and slightly over-weight, you may have benign intracranial hypertension). Again, a detailed eye exam should provide some answers. Read more...

Why does my vision blur when I put my contacts on?

Revisit your doc! If your vision blurs with contact lenses, it may be from either a bad contact, wrong prescription, or poor fit. In all 3 cases, you best see your eye doctor! Read more...