HELP! Duck with swollen eye!

[Ducklover3449]

Hello! I have a drake Saxony duck. I checked him out, and saw that his eye was a bit swollen. I thought it would just go away. But now, it has been a couple weeks and it is still here. One of his eyes has this pink bulge inside the socket, but it is beginning to poke out. His other eye is completely flat. I probed it gently, and it seems to hurt him. I see tear streaks forming around his eye area. I see no nasal discharge, and I use a saline wash on his eye everyday. (warm water with salt). I also put ACV in his bathing water to help disinfect it. It's been quite a while, now and still don't see any sign of improvement. What it makes it worse, is that it was bulging a mm or two out, so a small piece of grass managed to get in. I removed it, but the pink area of his was slightly bleeding, maybe just a strand or a drop. Can anyone please help me? I rinsed out all the blood and cleaned his eye well. Anything I can do that is inexpensive but effective? Thanks all.
Here is his eye: This is when I already cleaned it. My other ducks seem unaffected. Why did this happen? I let him bathe often, and give him free range when I'm with him.