I agree with Misty, usually just one cloudy eye is most likely an injury rather than disease, but not always. Are you sure the puffer is not picking on her? How big is the puffer? Puffers are nocturnal and could be harassing her after lights out. S&S puffers can be aggressive to slow swimming fish like angels, especially if the Koran was introduced after the puffer. The eye may very well be a wound. You can treat the eye with Epson Salt, I forget the dosage, I think one teaspoon to five gallons, but you might want to check on that, or I'll check and get back to you, because dosing Epson salt in the display can cause your Mg to rise if you are already dosing it. I would watch the tank from a distance in low light to see if the puffer is harassing the angel. If this is the case I would probably get the Koran into a hospital tank to treat. If the angel is still eating at all she will be easy to trap, but if you wait it will be harder, because it's hard to trap a fish that won?t eat. I have a trap and a hospital tank already cycled if you need help feel free to PM me. Unfortunately, one thing about Korans, once they start to go downhill they go quickly.