Very unfortunate situation, but I'm doubtful that it's the bacteria causing it. As far as I can tell, it just doesn't produce enough formate. The body is pretty good at metabolizing formate, so it really only causes blindness from large, acute exposures, not smaller chronic exposure, AFAIK. Combine that with no other reports of blindness from other users of the Lumina probiotic, nor any similar issues appearing in rodent studies, and the bar for evidence is pretty high.