Have you seen an ophthalmologist or whomever is treating you for the PMR about your sight loss?
Not trying to alarm you but often people with PMR develop temporal arteritis which can cause loss of vision. It’s treated quickly with prednisone.
I know you’re on that now but at a very low dosage. If this were me I’d make a phone call to my doctor ASAP!!
Did the vision loss start after you began the prednisone taper?