just another gosling
Join Date: Feb 2007
Location: Everett, WA
Bikes: CoMo Speedster 2003, Trek 5200, CAAD 9, Fred 2004
Mentioned: 19 Post(s)
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I've had this happen during long rides. I don't start getting it until around the century mark, and it doesn't always happen. My guess is that it's blood sugar related. Try eating a couple hundred calories of carbs immediately after the ride, and then keep eating over the next couple of hours. See if that helps. I have neither migraines nor headaches.
Another possibility is that your glasses aren't optically perfect. Try better/different glasses.