In a study, participants twice took capsules containing caffeine or placebo. Some experienced increased tear production (nothing whatever is said about the tear quality or whether their symptoms improved), depending in part apparently on genetic factors.
Those few measly caffeine capsules and what they did have been extrapolated all over the press to headlines like these:
Caffeine use may offer relief for millions of dry eye sufferers!
Caffeine intake: Give tears to your dry eye without a cry!
Put down those carrots! Coffee is what's good for your eyes!
Researchers discover simple dry eye treatment!
Drinking coffee may offer relief to dry eye sufferers, study says!
I'm not even going to bother quoting from any of these articles because I think the headlines are sufficiently indicative of the calibre of reporting. What the popular press distills from medical studies cracks me up. Reminds me of the stuff Hawkeye and Trapper used to filter through their dirty army socks.