Hi ya, i’m sorry to hear of your double vision. I know what a nightmare it is! I’m 23, I developed sudden and severe double vision when I was 20. Like you, i’ve never known what caused it. My gp would only prescribe deltracortril for two weeks at 30mg a day, and that’s only because I was very pushy. My vision was perfect on the steroids but my double came back, although nowhere near as bad. I’m still trying to get rid of mine! Your questions about what happened and will it ever happen again are ones that I repeat to doctors over and over…. But I never get any answers! If you don’t have any other symptoms, I think you are pretty safe, it's unlikely you have anything sinister going on – maybe it was viral. The only thing I can say to you is that I take omega 3 and omega 6 fish oil supplements in fairly high doses, these repair & protect your eyes extremely well from damage. I take them in a blend with vitamin e to help the oil be absorbed. My 3d vision actually improved a lot on these.