is this affecting 1 eye or both?
usually if it affects only 1 eye it is usually associated with the fish injuring its eye due to perhaps being shocked and while darting away it hit its eye against a rock.
so as with human wounds, such physical injury will heal with time...it is rarely fatal but if it gets out of hand, the fish may lose its eye
if both eyes are bloated, u've got a water parameter crisis
u can do a search on wetwebmedia for more info on this