It's like a headache behind the eye, but in my opinion, it's worse than an actual headache. It happens about once or twice a month, and all it is a pain behind the eyeball. I took some Tylenol and usually it helps but today it's not helping at all. I asked my optometerist a couple of months ago about it and he had no idea wtf I was talking about. I've got an appointment with the doc today so maybe he might know