You can use epsom salt (1 tablespoon per 5 gals) to relieve swelling if the "popeye" is due to trauma/injury. This is sometimes the case if it's just one eye... both eyes almost always means a bacterial infection has set in. And being epsom salt is just magnesium sulfate, it's reef safe. Just be sure the epsom salt is "food grade" i.e you'll see "USP" on the box. If it doesn't work, nothing lost... move on to antibiotic treatment.
