Well, in my opinion, you are not supposed to use eye drops as laxatives, for it will just be bad for your body. According to some researches, ingesting Visine can cause cardiac problems. What is more, it will just lead to more serious problems in your body. Anyway, just avoid using eye drops as laxatives.
Certain kinds of eye drops can make people poop, but I do not think that you can use eye drops as laxative. When a kind of eye drops are taken by someone as laxative, he will poop more, but at the same time, the ingredients in the eye drops can also cause great damage to body such as diarrhea and even dehydration. Some chemicals in the eye drops are very poisonous. Some people even use eye drops to commit murder. Besides, according to the instruction, eye drops are drugs for external use and cannot be taken through mouth. As the name suggests, it can only be applied to eye problem. If you have constipation, you should buy laxative in the nearby pharmacy.
Maybe some kinds of eye drops could be regarded as a laxative. You need to read the instruction of the eye drop to see whether the material of the eye drops is same as laxative. However you should not mix them which may be bad for your health. You need to deal with these two things differently. You should not use such things casually.