So sorry to hear that you can no longer drive and of your worsening eyesight. I can't drive due to fainting and severe blood pressure problems so I totally understand how horrible it is, particularly when you rely on a car so much like me.
I'm in the UK and things are similar here in terms of MRI scans. We can't just go and demand one. Doctors will only order one if they feel its absolutely necessary... and even then they only do them as a last resort.

SO annoying. I hope you manage to find a doctor to order one for you asap, really sounds like you need treatment.
Hoping things get better for you soon