Speaking for myself, you rarely have the same experience with you. It seems that tearing while laughing is strange, don't you think so? But you shouldn't worry about it too much, because you gotta bear in mind that different people have different body types right? So, shedding tears while laughing , if the tears cannot fill a pool, is normal. But if you have several other uncomfortable feelings in the mean time, then it is possible that you really have something wrong with your eyes. Anyway, may you good health and perfect vision.