Rinse the eye with Saline solution and apply the eye ointment the vet gave you. I've used the same ointment to treat everything from the dog to my kids to my chickens. Just got a new tube from the vet when some of my chicks started getting only the left eye swollen and infected. She also told me I could also use Neosporin in their eye. It took about two weeks for my two sick-eyed chicks to clear up and I kept them separated from the rest because it seemed contagious.
I originally found four sick chicks - all with left eye swollen closed and infected but two also had a massive infection/growth in roof of mouth and could not close mouth. I had to cull those two. The other two mainly had the eye problem with just a little bit of crud in crack of roof of mouth so I cleaned that out wih q-tips and/or toothpick and shoved Neosporin up into crack. Both chicks made a full recovery and were reunited with the flock after two weeks. No one esle has come down sick.
Be sure and check the roof of the mouth. I think the sinuses, when infected, drain there and can block it up.