HUH? Copper for a cloudy eye? Correct me if I'm wrong, but wouldn't a cloudy eye more likely be a bacterial infection? I don't think I would go dumping copper in there just yet. Whats the temp., PH, and sal. If those are all within range, and the fish still looks bad(are there any other signs of illness, besides the eye?), I would try antibiotics of some sort. One of the sharks can probably give you a better recommendation than I can, I have no experience with lionfish(yet

) I just didn't want you to go medicating your tank for the wrong illness.
HTH
B