Popeye, or exophthalmia, is swelling of one or both eyes of the aquarium fish. It is difficult to treat but easy to prevent.
Popeye Identification in Fish
One or both eyes of the aquarium fish bulge outwards, hence the “popeye” name. The outer surface of the fish’s eye may be white or cloudy. Popeye can be referred to as unilateral (just one eye affected) or bilateral (both eyes affected).
Popeye is unlikely to be confused with any other diseases in fish.
Popeye Pathology in Fish
The swelling of the fish’s eye is caused by tissue fluid leaking into the region behind the eyeball. Pressure builds up as the amount of fluid increases, forcing the fish’s eyeball outward. Opportunistic bacterial infections commonly occur. The cloudiness of the fish’s eye is caused by damage to the cornea (the transparent layer of skin that covers the pupil).
Popeye in fish is most frequently caused by continual exposure to chronically poor (rather than acutely lethal) water conditions. Popeye is consequently most common in aquariums that are overcrowded or receive infrequent water changes. Not surprisingly, popeye is most often seen in aquariums where messy fish are kept in unhygienic conditions, typically goldfish and large cichlids.