flyerNy

I don't think migraine auras are that rare. I have friends who get them and I have had them, but only twice ever in my life. If it is a rare occurance I am sure it won't be an issue. Though there may be many causes, you may be able to find the reason for the aura and try to avoid it. I was on the computer all day once and got an aura. I sucks when it happens. Second time it happened I ran to the Eye Doctor (being a pilot drives major concern about vision). With a thorough evaluation he said my eyes are fine 20/20, nothing wrong with them and what I described was a migrainal aura. He said that it is not an issue with me and flying because they are so rare (twice in 6 years). He used to be an Aviation Examiner. He did not seem concerned about it. If it happens often it maybe be an issue though.
For those that don't know, the aura is annoying and is slightly off-center of the vision(looks like psychedelic flickering). It lingers for about 10 to 15 minutes in both eyes as the migraine messes with your central nervous system. Shortly after you get the headache and aura is gone.
No human is perfect. Everyone has some sort of issue with regards to aviation medicals, and if they haven't they will. It is largely up to the Pilot to determine when they are not safe flying, you know your own body.
From what I experienced, I did not think they were bad enough to interfere with flying duties and it only lasted a few minutes (though I was not flying at the time).
I did think about what actions I would take if it happened in flight and did interfere with flying. The only portion of flight where I think it would be most critical is approach and landing. If it were to happen at that segment of flight I would simply wait the few minutes for it to go away before beginning that segment of flight. From my experience they do not seem to just appear but rather grow in size slowly, further they don't seem to be that large that you are blinded, they simply restrict a small area of visual field. Therefore it is not like you will be flaring and then suddenly get blinded and crash. By the time you first experience it coming on during an approach, you will already be at the car when it is full scale aura. Though if it were an issue during approach, go missed and go around. By the time you come back it will be gone, though the headache may suck. If I were you and was this concerned about the aura's I would first speak with a regular doctor. From there go to an AME. See what they think. Then when you make it past them in approval, think about what you will do and actions you will take, should it happen in flight. Talk to a good CFI.

Remember, nobody is perfect.