My dog has developed swelling in his eye. It is nearly shut with elevation, and no discharge.. Initially there was some tearing and it worsened over the last 2-3 days. There is no discharge. My dog Does not seem to be in any kind pain, but he is quiet and sleeping a lot. We have difficulty with his diet. He eats primarily people food ( meat) . He did have about 3/4 cup of cut up pizza around the day it started. We are calling a local veterinarian first thing in the morning. What could this be?