Popeye can be caused by damage to the eye, such as by using a net to move the fish, or even by scraping against a rock. I would remove the fish to your hospital tank (you do have one, right?), and treat it with a broad spectrum antibiotic. It is unusual for a fish with this problem to refuse food unless it has the problem in both eyes, and is completely blind. In that case, survival is doubtful. Get the nitrates down with water changes, and if it begins to rise again consider reducing how much you feed. Be sure to check on ammonium levels so that you know that the tank is not going through a short cycle, which will damage the fish. I have had fish recover from this, especially an emperor angel who lived for 5 years after even though he was clearly blind in one eye. When he died (during hurricane Sandy he was 15 years old, so don't give up on the fish.