“What can be the cause of blurred vision?”

tons of things...
some easy to fix, some not so easy...

There are too many reasons that your vision can be blurry, but I can name a few. Myopia, astigmatism, presbyopia, and hyperopia can be corrected with glasses or contact lenses. Cataracts may be a reason for blurry vision depending upon your age. Medications can cause blurry vision. Diabetes can cause blurry vision as well as many other medical conditions. Cornea and retinal problems can cause blurry vision. There are neurological and vascular conditions that can cause blurry vision. I would strongly suggest that you see an eye doctor so that you can know the source of your blurry vision and what your options are in order to treat or correct the problem. Good luck and best wishes.