My cat, (cross bred persian, 3 years old, have him since 2 months or so.) always has some kind of tearing eye, leaves a brown stain right under his right eye.

This seems to be a known problem. Already found some info about this at another site, but no real solution. Also tried different brands of food, doesn't change either. Any ideas? Should I take him to a vet? He doesn't seem to have very much problems with it, his right eye doesn't look all wet or anything, I usually clean his eye once a day.