Those who have supposedly suffered the runs from eyedrops and see this as confirmation of food tampering as a regular occurance may have to consider another cause.
Les, yesterday I went to the Snopes site and saw the same thing. Yes, Snopes says the reports that Visine (the brand cited, as others aren't mentioned and perhaps some ingredients vary) causes diahrrea are
false.
However, as the remainder of your post shows, the results of ingesting Visine can be dire.
Idiot or not, any threat that someone might resort to such trickery should not be taken lightly.