I have a different course of action, if I may be so bold. If it is pop eye or cloud eye, it can cause permanent blindness in the fish if not taken care of. While it may be true that your fish can heal itself, that is not always the case. If it isn't showing significant improvement in two weeks, I would prepare a small amount of tank water in a bucket (say a gallon or two) and prepare a treatment of Melafix. Catch the fish and dip him in the bucket of Melafix treated water for about 10 minutes. repeat this regimine every other day for a week and it will go away.
Again, wait it out for 2 weeks, and then dip it. Just my :twocents:
-Doc