it started slowly.  At first i didnt even really know that the burning wasnt normal.  Drops twice a day.  it feels like sand in the corners of my eyes.  My eyes feel so heavy and I just need to close them.  Ive been commuting for an hour each way to work for over 20 years and its never been a problem until now.  Now I cant make it more than 20 minutes without feeling like I need to close them.