being happy really isn't a good sighn to determine illness on, it could be pop eye, if its not bothering him much that may mean its juts in its early stages, u should treat him with melafix and catch it early if thats wat it is
Generally it is a sign of popeye, but I have a betta who is naturally coloured with light circles around his eyes... I guess you could go ahead an treat it. Better safe than sorry