This is a duplicate of my Dry Eye Digest blogspot blog - to see the full archives back to 2005, please click on that link.
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 to treat dry eye symptoms"