I have suffered with dry eyes for about 3-4 years. Even developed a corneal ulcer to begin with which was excruciatingly painful. I had to wear a 'bandage' contact lens for a month to get it to heal, because my eye was so dry. They tell me it's caused by nerve damage, more so in my right eye.
Along with this I had a condition called filamentary keratitis, which is basically little strands of skin/mucus attached at one end to the cornea - caused by a poor quality tear-film - and again, unbearably painful every time you blink. My cornea was so inflamed that I could only read the top letter of the Snellen chart.
I had a whole barrage of treatments to try and clear this up and it is now much easier to manage. One thing that seems to set it off again is if my BGs go into double figures so, as others have noted, getting your BGs under control is the best solution.