Popeye's disease – also called exophthalmia – is not an actual disease, but rather a condition in which the fish's eye is swollen and protrudes abnormally from its socket. This problem can affect a single eye or both eyes. Eyes may be cloudy or even appear clear in some cases, aside from the obvious swelling. If you see one or more of your fish showing signs of Popeye, there is a chance that there is an underlying infection behind the scenes. One that can cause your fish to lose its eyes or vision if left untreated.
But just because a fish has large eyes doesn't mean there's a problem. Some breeds of fish – such as the Black Moor Goldfish and Celestial Eye Goldfish – are prized for their large telescopic eyes, which are perfectly normal and healthy.
Symptoms of Popeye's disease in aquarium fish
Fish breeds that do not normally have telescopic eyes can sometimes have significant swelling of one or both eyes. This swelling is usually caused by fluid entering the area behind the eyeball. The eye may be cloudy or discolored if the cornea is torn, or it may be stained with blood (in the case of physical injury to the fish). Popeye can be bilateral or unilateral. Affect both eyes or only one eye. In severe cases, the eye can rupture without treatment. In this case, the fish may recover but be blind in the affected eye.
Causes of Popeye's disease
Multiple agents can be responsible for popeye, and sometimes the true underlying disorder is never determined. If only one eye is affected (unilateral), it is likely that the condition is caused by an injury rather than a problem with water chemistry. This is especially true when only one fish exhibits popeye. A swollen eye may be the result of a fight with another fish, or your fish may have scraped its eye against an abrasive object in the tank. In this case, look for damage to the eye – a dead giveaway that exophthalmia is the result of an injury. In most injuries, the protruding eye will recede as it heals. However, the fish should be monitored closely as infection can occur, causing the fish to lose sight in the affected eye.
Another cause of popeye is infection. This is most likely to be seen in both eyes. The infection can be caused by a variety of organisms, including bacteria and parasites. If the fish has both Popeye and dropsy (edema of the abdomen), the prognosis is grim. Internal problems such as kidney failure or metabolic problems can cause fluid buildup and make treating your fish extremely difficult. Poor water conditions may also contribute to popeye and sensitive fish being affected first. If one or more fish in your pied present with Popeye, test your water to determine if something is wrong with its chemistry.
The treatment of pop eye depends on the underlying cause. If the eye has been injured, perform palliative care with aquarium salts while the eye heals (unless contraindicated). Regular water changes and monitoring of water chemistry is also recommended during the recovery period. If water tests indicate a problem – a drifting pH or elevated ammonia or nitrite levels – correct it immediately to avoid additional stress. All fish should be fed high quality foods to support a healthy immune system. Any fish that is clearly suffering from a bacterial or parasitic infection should be placed in a quarantine tank to avoid infecting other fish. Treat this fish with a broad-spectrum antibiotic recommended by your pet supplier to eliminate the infection. If more than one fish is infected, the main tank may also need to be treated with antibiotics.
How to prevent Popeye's disease
Since popeye is caused by a variety of problems, there is no magic bullet that will prevent its occurrence. However, if the tank is well maintained, water changes are performed regularly and the fish are fed food. However, the likelihood of the popeye becoming noticeable is greatly reduced. Monitor tank chemistry and watch your fish daily for signs of disease to tip the scales in your favor. If basic care is carefully followed, Popeye is unlikely to occur. And if, then it is probably not deadly.