I've been dehydrated a couple of times and never had floaters and didn't have them in my U.C. days when anemic either. However, I have had what I call "stars" or flashes of light with migraines. Sometimes I get the migraine aura which affects vision. Sometimes even without the aura, my vision isn't as acute when I'm getting a migraine. When the migraine clears, my vision is back to normal. Am wondering if your severe headaches could be migraines.