There are other things that can cause swollen eyes, chickens can get eye infections/pecks/injuries as well. However, adding gaspy breathing, bubbles in the eyes, sneezing, etc - that usually points to a respiratory infection. They CAN recover, however they will always be carriers and the disease will pop up again if the birds are stressed in some way (weather, new chickens, handling, new dog, whatever). Wild birds can have it, chickens and eggs you bring home can have it, you can even track it around on your shoes. =(
You CAN treat for this, just know that you can't sell or rehome any birds and any new birds you bring in will get it too. So if you don't cull and decide to treat, you have to have a closed flock.
Question...... When I first bought my ready to lay pullets I didn't quarantine the 3 different farms worth of chickens that I picked up all on the same day......my mistake. There was an outbreak and I treated them and everyone seemed good. They had the open mouth breathing.....and sneezing/cough their eyes were clear. Then a day ago I noticed one that was open mouth breathing again and this has been about 4 weeks after the first outbreak. I have not added any new chickens so I wasn't sure why it was triggered again. We are okay eating the eggs from these hens as long as we are not medicating them correct????