Blurred vision that is often caused by minor eyestrain or allergies will go away on its own. Refractive errors can be easily treated with glasses, contact lenses, or surgery. Sudden blurred vision may be a warning sign of a serious medical condition related to diabetes, heart disease, stroke, glaucoma, eye injury, or other factors. If your vision suddenly becomes blurry with any other simultaneously occurring symptoms, you should always seek immediate medical help.