What to do if my eye vision 20/1500 how bad is that?

See an eye doctor: There is a reason why your vision is that bad. You must see and eye doctor to determine why and to see if it can be corrected.

Depends: If this is your uncorrected vision, then get measured for eyeglasses and hopefully you will achieve 20/20. If 20/1500 is the best you can get with that eye, then there is probably an important pathology limiting the vision which an ophthalmologist can diagnose and hopefully treat.