What Causes A Feeling Of Something In Eye With Small Crystal Formation?

This is an intermittant problem with my left eye. My wife has the same problem, and a friend who works for me is also complaining of similar symptoms. My left eye feels as though there is an eye lash or some particle in the eye. I had my eye examined by an eye doctor who ruled out pink eye and could see nothing in my eye. It appeared when too little sleep. I notice that sharp little crystals seem to form around the base of the eye lashes. I think one of these get caught in the eye, causing the irritation. My wife has also noticed tiny crystals forming at the base of her eye lashes. Any idea what possible causes for this?