First of all, I have taken dd to the doctor about this, her response was to say "well that is very odd" and then leave! (I have given them a very clear photograph showing the colour difference.)
I have now asked for it to be referred to another doc and am awaiting a response, in the mean time I was hoping that someone would have some experience of this very odd occurrence as I can find nothing out on the internet - not even really scary stuff!!
Basically my dd (12) has brown eyes but every now and again one eye (the same one each time) turns vivid green! The effect lasts anything from about 10 minutes to a few hours but it always changes back again.
Dd does suffer from hemi-plegic (sp) migraine which I suspect may be connected but I have no evidence for that, just a gut feeling!
So, has anyone come across this before and have any thoughts for me? I am unsure how serious I should be taking it as the doctor was really very dismissive and just seemed to find it amusing 
No amount of googling is giving me any help either!