Twice when I have been on a plane, as we start to land, I have experienced excruciating pain in my head ....?

...just above my left eye. The only way I can describe it is as if someone is digging a knife into my brain. It's so sharp and severe. It makes tears pour out of my eyes, not because I'm crying, but from the pain. Similar to when you get hit on the nose and water pours from your eyes. Does anyone know what can be causing this and if there's anything I can do to prevent it. It's really frightening. I thought I was going to die the first time it happened as it was pain like I'd never experienced before. The air stewards were pretty useless both times and told me to take deep breathes.