It is so wired that your eyesight changes from day to day. I never meet such problems. You shall get your eyes checked from doctors. And a major thing you shall check out is your blood sugar. Check the stability of your glocose levels throughout a day and from day to day because unstable blood sugar is notorious for causing fluctuations of vision.
Constant eyesight changes can be caused by many factors like aging, Presbyopia, Diabetic retinopathy, Macular degeneration, Cataracts, Floaters, Presbyopia, eye infection, retinal detachment, migraine headaches, optic neuritis, brain tumors, stroke and bleeding in eyes. It may also indicate a sign of certain eye disease. I think you should always get it checked out, especially when there is a problem in your eyes.