Chicken has injured eye

[FloydLucy]

I'm just wondering if anyone can help. I have a chicken which looks like it has been attacked. His left eye cannot be seen and is a large bulbus mass. It has puss leaking out. The chicken seems fine, he is eating and drinking and runnig around. There seems to be nothing wrong except for the injured eye. Does anyone know how i could treat this injury.
Thankyou