my mom and bro had it in thier cranial nerve, leading to eye, but the mom had no permanent damage surprsingly enough given her age and health, which makes her somewhat susceptible to severe infection. there was scarring found in the bros sclera though.

zoster keratitis, i believe can cause blindness if it affects the cornea, the most extreme is needing a transplant. the other severe ones, is hearing loss if it affects the ear, and spinal and brain meningitis.

mines did reach the spine(undiagnosed) i knew something was wrong when i couldnt bend my back normally. its not considered severe if you have no neurological symptoms(vomiting , photophobia, severe headache)