puffed eyes are not a disease itself, its just a symptom. It could be a result of some patogen or parasite working its way in your fish, but most likely cause is inadequate water condition.
Can you describe the situation better? How big is the tank, who else live there, how old is the setup and fish, what is temperature, light, and water change regimes, what do you feed your fish.
If you can, tell exacttly what temperature, pH, ammonia, nitrite, nitrate you tank has.
Most likely you just screw up with water chemistry and your fish is suffering because of it and got some kind of opportunistic infection. So check and adjust the water quality. Everything should be back to normal in 1-2 weeks once you fix the water. Seriously, in aquariumistic 99% of all problems is water quality.