it there congestion , sneezing, scratching at the head, and or head shaking?
Swollen eye not as a result of injury is almost always MG, Mycoplasma gallepsum. It is chronic meaning the bird will always be a carrier of it after it gets better. Infected birds usually show signs of it for 1-2 weeks, then within days it'll get better, no meds will fix it, they will help keep it from getting other infections, but not sure it (it's also referred to as Chronic Respiratory Disease too)
I hope that's not the case, as a bird with it will be able to infect all other birds it comes in contact with for the rest of it's life. While not overly fatal, it is a problem you dont want to have in your flock or to sell to others. One other thing is it is passed from hen to egg too.
If swollen, yellowy mucus knot in it, thick liquid oozing out around it, these are the most common signs of it, though it takes a test to confirm, yet it is VERY common especially in peafowl and turkeys.
By the way, if it does develop a mucus ball under the eye lid, you will need to get it out or it can turn hard, ball shaped and blind the bird.