Auto immuno deficiency virus + blindness
Exhibit A) HIV+ screws up your immune system.
Exhibit B) There are diseases that attack your nervous system.
Can a HIV+ person be attacked by a virus/bacterium in such a way that blindness ensues?
I was originally thinking of dyslexia, which mkaes you wtrie lkie tihs. But any visual impairment would (sort of) do, so long as it prevents writing by pencil-paper.
Googled dyslexia, blindness, AIDS. Got nothing except loooong flame wars about AIDS denial.