Just to give you a personal experience - I used to get very bad migraines with blurry vision and this most often was triggered by extraneous exercise. I would run for long periods of time my face would turn white and after a while I developed migraines.
This may have to do with the high demand of oxygen your eyes and brain require and when forced to the limit during exercise you can experience bad headaches etc. I was also diagnosed with mitral valve prolapse and may have direct connection to these migraines.
Also you may want to look at his dental work done prior to these episodes. Things like root canals can certainly trigger these kind of symptoms and most often the link goes unnoticed.