Cirka en matsked i maten eller vatten om dan. Pigs often have watery eyes, and they need to be cleaned. Try to use babyoil instead of water. If you clean around the eyes often, the water can make the pigs skin dry. And the oil dissolve dirt effectively.
Cider vinegar can help a great deal against watery eyes.
Use one tablespoon in food or water every day. It may not eliminate the problem completely, but it will probably help. Besides, the Vinegar has a good effect on many other things. Put something your piggy like in a paperbag, and wrap it together. The pig now will have a good time of activity when trying to get to the contents of the wrapping.