There are many possible causes for blurred vision. As you say it comes and goes, you are most likely to have blood pressure problem or diabetes which is also related to blood pressure. When you blood press goes up or down quickly, blurred vision will occur.
Also, blurred vision is a sign of many serious eye diseases such as glaucoma.
Lastly, your blurred vision may be caused by dry eyes. If so, you may suffer from other dry eye symptoms like red eyes, itchiness, and pain.
You must pay attention to your symptom due to it can be a signal to indicate the changes in your body. Our eyes are highly connected to our nerves so that they are sensitive to our body diseases. As we all know, permanent or sudden out of sharp vision can announce the presence of eye diseases. Blurred eyes can be the complications of the some eyes surgery, like laser surgery, or eye inflammations, as well as a side effect of some medications. So if you are just experienced a surgery or some eye diseases, such as eye dry, eye pain, watery eyes and goopy eyes, you need to go to see your opticians immediate to see if your eyes are in trouble and need medicine for emergency relief. Besides, you need to get an exam to see if your glasses degree is not enough now. You can do it in an eye office or retail location costing you extra money for their service. If you let things slide, it can lead to eye blindness finally.
In most cases, blurred vision could result from infection,inflammation, trauma, and other diseases. By the way, blurred vision can be a symptom of increasing ages. In rare cases, wearing contact lenses for a long time may cause blurred vision. In my opinion, you should go to see a doctor and find the reason why you get blurry vision. Then get professional treatment.
As a matter of fact, blurred vision may begin all of a sudden and then disappear quickly. This is normal depending on the causes that lead to blurred vision. Forex ample, when your eyes are refocusing on a far object after sun overexposure, it may cure itself suddenly.
In order to avoid blurred vision, we should protect our eyes from harm. Leading a healthy life style and using eyes properly can be of much importance.