I had PMR 2015 for about 2 years , weaned off Prednisone and I thought I was OK to get on with "normal" life.
I am now 80 . August 2022 , I developed really strange symptoms in my throat , jaws and tongue. I could not eat properly and my teeth seemed to be out of alignment. I consulted my dentist but she couldn't come up with an explanation.
Then about a week later, I suddenly had severe pain in my right eye socket and double vision. which lasted for about 10 mins. I contacted my GP [ doctor] and he told me to go to emergency dept. Can't remember why but I delayed for 24 hours . It happened again the next morning. This time I went to ED at my hospital where I was admitted straight away and given 3 daily infusions of 100mg prednisone. I also had surgery for a biopsy to be done on my temporal artery near the eye in question. it was positive for LGA [I am in Australia].
So , yes it was very sudden , no warning except for the jaw problems .
Now 16 months later I am being weaned off the prednisone [down to 6 mg] but I understand that I could regress any time. My eyesight is Ok but like you I am terrified when I think about the prospect of becoming blind even in. one eye.
To go back to 2015 when first diagnosed with PMR I was warned about LGA but I did not take it seriously enough.
I was lucky to have excellent and immediate treatment . My rheumatologist considers it serious enough to give me his mobile no. and insists that I present myself to hospital asap and for drs there to contact him immediately.