I lost vision in my left eye last month. I went to Mayo and was told it was NAION. I am still in the learning stage. I don't have any of the risk factors except I have no cup on either eye. My ratio was 10: 0.0 . I am following up with my doctor for a sleep study. I don't think I have sleep apnea but I figure the only way to know is to do the study. How may here have low or no disc to cup ratios?