The cause of my migraine a few years ago was bright lights hitting my eyes.  I 
always wore darkglasses.  Sun or light hitting shiny metal or car tints with 
sharp light reflection or the bright summer sun would cause me such horrible 
headaches that gets worse if I moved my head.
 
A brother in law was seeing docs and when he told me no one could find the 
cause, I told him to wear dark glasses.  Sure enough it went away when he used 
goggles.
 
Lack of Vitamin D also causes headaches.
 
Melly