I have a hunch, that eye looks like the work of tematodes. If it is trematodes, copper has absolutely no affect on this parasite.
Get some tap water (freshwater - 1/2 gal or so) about the same temperature as the aquarium, add dechlorinator to remove chlorine from the water, put the angel in the fresh water for about 10 minutes. If it is trematodes, you will see the parasites start to turn white and eventually they will fall of. The parasites will kind of look like scales falling off, this is a fairly large parasite.
When you dip the fish, it's body will bend, it will lay on it's side and look pretty bad for the first few minutes. Don't panic, leave it in the fresh water for the full 10 minutes.
As long as the fresh water that you dip the fish in is close to the same temp and PH as the aquarium, it is not a very risky procedure.
Try this and report back what you see, from there I will have a better idea what your dealing with and can advise on what next to do.
Joel