There have been many instances of tramatode infestation here lately, and the fish are coming from various wholesalers, all infected, so we aren't just blaming "one" supplier. They mainly infect tangs and angels, but I've seen many other species infected too.
It's a parasite. It infects the gills and the eyes, and it's rather alarming when you see the end result.
I'd FW dip the Flame angel, for 5 minutes in RO or dechlorinated tap water, at similar temp to the tank. Give it the full 5 minutes, because often it takes 2 to 3 minutes for the parasites to die, and then they fall off. When you do this, you'll see what looks like sesame-seed sized things fall off the eyes, and often blow out the mouth and gills. I've seen dipping containers that look like snow globes by the time the 5 minutes are up
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I'd try this before any medication. I'd do it once today for 5 minutes, and once tomorrow for the same. IF tomorrow's dip comes up clean (no "sesame seeds"), then you got it. If there is evidence in tomorrow's dip, do it again the next day until it dips clean. Usually one or two treatments gets them unless a tankmate is reinfesting.
Popeye is a bacterial infection, and the symptoms are swelling, not that opaque "plastic" like cataract-ish thing you are describing.
IF a dip doesn't yield dead parasites, THEN rule out what I've suggested and look at medication. The 5 minute stress of a FW bath will most likely save you the cost and stress of medicating if it's not necessary.
I've yet to lose a fish to a FW dip, and through my work I've done dozens of 'em.
HTH
Jenn