Why do I keep having eye pains?

For years every now and again my eyes will go blurry with or without a headache/migraine. Sometimes I can't even see. I also keep having sharp pains begin one or both of my eyes and my head doesn't hurt, so it's not a migraine. I don't know what's wrong. I've had my vision tested before and it's almost perfect. What could this be? I've heard some people say they had these type of pains with tumors. Or could it be dry eyes?? Thanks for the help in advance!!