Popeye Disease in Aquarium Fish

Popeye disease is a condition in which a fish's eye swells and bulges from the socket. The eyes may also appear cloudy. When left untreated, popeye disease can cause a fish to lose its eyesight or even result in the loss of an eye. Fish popeye has several potential causes, including infection, injury, and poor water condition. You can usually treat popeye in fish, but the treatment depends on the cause.

What Is Popeye Disease?

Popeye disease—medically known as exophthalmia—is a condition where the eye of the fish is swollen and protrudes abnormally from its socket. Note that some species of aquarium fish, such as black moor goldfish and telescope-eye goldfish normally have protruding eyes; this is not the same as popeye disease. Fish popeye can affect a single eye or both eyes. The fish's eyes may also appear cloudy in some cases.

Symptoms of Popeye Disease

The defining symptom of popeye disease is one or both of an aquarium fish's eyes bulging from the socket. The bulge might be subtle, especially early in the disease, or can be quite striking with the entire eye and socket appearing extremely swollen. Depending on the cause and severity of the popeye, the fish may show other signs of illness as well.

In fish species that do not normally have protruding eyes, popeye starts with a subtle bulging of one or both eyes. This is caused by the pressure of fluid leaking into the area behind the eyeball. As the condition progresses, the bulging can become quite pronounced and lead to further symptoms. If the swelling ruptures the cornea, the eye might appear cloudy, bloody, or discolored. In severe instances, it's possible for affected eyes to rupture completely. If this happens, the fish may eventually recover but will be blind in the affected eye.

The fish might also show systemic signs of distress, such as changes in behavior—a formerly active fish now hides or stays near the bottom of the tank, for example—or a loss of appetite displayed by not actively pursuing food. You might also notice your fish keeps its fins clamped against its body, its scales look raised or rough, or that its entire body appears somewhat swollen.

Causes of Popeye Disease

Multiple causative agents can be responsible for popeye, and sometimes the true underlying disorder is never determined. Most commonly, fish popeye is caused by an injury, an infection, or poor water conditions in the aquarium.

• If only one eye is affected (unilateral), it is likely that the condition is caused by an injury rather than a problem with the water chemistry. This is particularly true if only one fish in a community tank is exhibiting popeye. A swollen eye can be the outcome of a fight with another fish, or your fish could have scraped its eye against an abrasive object in the tank. If this happens, look for damage to the eye—a dead giveaway that exophthalmia is the result of an injury. In most injuries, the protruding eye will eventually recede as it heals. However, the fish should be monitored closely, as infection can ensue, causing the fish to lose sight in the affected eye.
• Another cause of popeye is an infection. This is most likely seen in both eyes. Infection may be caused by a variety of organisms, including bacteria, fungi, and parasites. If the fish suffers from both popeye and dropsy (edema of the belly), the prognosis is bleak. Internal problems, such as kidney failure or a metabolic issue can result in fluid build-up, making it extremely hard to treat your fish.
• Poor water conditions can also contribute to popeye and fish that are sensitive will be affected first. If one or more fish in your tank presents with popeye, test your water to determine if something is amiss with its chemistry. Also consider supersaturation of gas in the water, which can be seen as tiny bubbles on the sides of the aquarium and even in the fish's skin. This can cause gas to accumulate in the eyes and make them swell.

Diagnosing Popeye Disease in Aquarium Fish

There are no diagnostic tests or procedures used to determine fish popeye. Rather, you can diagnose it yourself by the characteristic symptom of bulging eyes on a fish not specifically bred for this trait.

Treatment of Popeye Disease

Treatment for popeye will depend upon the underlying cause. If the eye has been injured, it will typically heal on its own, as long as the fish does not develop a secondary infection or become stressed. You can help the fish recover by performing palliative care using aquarium salt while the eye heals (unless contraindicated). This helps to relieve the swelling. You should also remove any tank decorations that might contribute to further injuries, such as rough or sharp rocks, pointed plants, and decorative items with rough or pointed edges.

Regular water changes and the monitoring of water chemistry are also recommended throughout the recovery time, as poor water condition is a common cause of popeye, as well as other fish ailments. If water tests indicate a problem—a drifting pH or elevated ammonia or nitrite—correct it promptly to avoid additional stress.

Any fish clearly suffering from a bacterial infection should be moved to a quarantine tank to avoid infecting other fish. Treat this fish with a broad-spectrum antibiotic recommended by your pet supplier or veterinarian to resolve the infection. If more than one fish is infected, it may be necessary to treat the main tank with antibiotics, as well. And all fish should be fed high-quality food to support healthy immune systems.

Prognosis for Fish With Popeye Disease

Luckily, as long as you take steps to correct or eliminate the cause of the popeye disease, your fish is likely to make a full recovery, particularly if the condition was caused by an injury. However, if infection or water imbalance is to blame, and is not addressed promptly, your fish may lose the affected eye, or even succumb to stress or infection.

How to Prevent Popeye Disease

Because popeye is caused by such a wide variety of issues, there is no magic bullet to prevent its occurrence. However, if the tank is well maintained, partial water changes are performed regularly, and the fish are fed nutritional food, the odds of popeye striking are greatly diminished. Monitor the tank water chemistry and observe your fish daily for signs of illness to help tip the scales in your favor. If basic care is followed meticulously, popeye is unlikely to occur. And if it does, it probably won't be fatal.