Many have had their dreams of flying spoilt by poor vision, and many have got over it and gone on to do something they love and enjoy, even though at the time it may have seemed like the end of the world as flying is all they have ever wanted to do.
I cant see why you would fail? -6 is the limit, you fall in this. If you can see 20/20 with correction, you should be ok.
Dont matter whats in you frames, it matters what the AME optician thinks should be in your frames.
My optician got me .25 of a dioptre higher than the ame got me.
My issue was not perscription in the end, but the ability to read the 20/20 line with correction. Maybe too many years of tv and computer messed my distance vision up...