Common Names: Pop-eye
Salinity: Freshwater
Description: "Pop-eye" is a symptom rather than the name of a legitimate specific ailment and there are many causes that can produce swelling in the eyes of fish.

Swellings may be either symmetrical or asymmetrical, and in either or both eyes, often with reddening, and misting or discolouration of the eye. While rarely directly fatal, any injury to the eye is serious as it may impede the ability of a fish to track down food, and often more importantly in those situations with territorial fish, reduced vision renders the fish incapable of defending itself. Fish with pop-eye are often persecuted by others. Any fish can get a swollen eye, but for various reasons, usually to do with conflict or rubbing eyes on abrasive surfaces, cichlids and freshwater puffers tend to be the most often afflicted fish.

In the absence of disease, the most common cause is nitrate saturation of the water, usually at levels above 60 ppm. The more nitrate sensitive the fish is, the more likely it is to suffer pop eye under less than desireable conditions.

Fish with osmoregulatory issues and hepatic damage may also accrue liquid within the eye making it swell vastly out of proportion.

External parasites may also trigger bouts of drop eye, flukes and trematodia may burrow into the eye, and cuase damage as they feed and reproduce,and infections of velvet, gold dust disease, and whitespot if local to the eye can also cause pop-eye.

Multiple species of bacteria and fungus may invade an eye that is injured, abraded or suffering from acidity burn from inaequate water conditioning, and the fish's body will respond to infection by flooding the area with immuno cells and fluids often causing the eye to vastly swell. Bacterial and fungal necrosis often finally ruptures the swollen eye , leaving the fish effectively blind and vulnerable to infection of the optic nerve, and this in turn can lead directly to infections of the brain cavity, which are usually fatal. Many fish survive ruptured eyes, but of course the keeper should strive not to allow the eye to be lost.
Symptoms: Spots
Treatment: Treatments for the various individual causes of eye infection are listed in the appropriate profiles, but the keeper will have to do some investigative work to establish what the cause may actually be. Once water tests have established whether or not the cause is high nitrate exposure, your odds on causes in order of frequency are:

1) Bacteria assosiated with wounds or abrasion.
2) Fungus.
3) Protozoan parasites.
4) Flukes
5) Osmoregulatory issies due to hepatic failure and general failure of the renal system.

Rarely supersaturation of gas in the water may be at fault, occassionally co2, but more usually oxygen. This is however, a rare occurrance in the world of usually rather overstocked, underfiltered, and under aerated amateur fishkeeping.

Should the causes be of bacterial , fungal or parasite in origin it is worth mentioning that the eye itself has barrier tissue, and is osmotically protected from medications introduced into the water, so any contagion already within the eye will not necessarily be reached by water administered medications , and this is often why dips and water administered medications are not especially effective in a number of cases. Filamentous growths like fungus, and occassionally , early stage columnaris, that protrude beyond the eye surface are sometimes successfully killed by expose to water administered meds, but others may be much more invasive and difficult to treat.

While the fishkeeper generally has little option with tiny fish except to use water administered meds and endure the haphazard results, with larger fish the treatments can usually be ingested, or even injected, ensuring that the pathogens are attacked from within and successfully eradicated. This also ensures that diseases which attack the renal system are handled directly, often neatly solving a number of osmoregulatory issues that may have a compound effect on the state of the eye and on the the systemic health of the fish itself.

Ultaviolet sterilizers will massively reduce incidences of eye infections of nearly all types.
Comments: Prevention is the best cure. Ensure quarantines are observed, and water conditions are kept sparkly clean and low in nitrates. Many fungi, protozoa and bacteria that will infect eyes are supported by detritus and uneaten foods in the tank, so keep on top of your gravel cleaning and water changes. Take special care that cichlids are kept in top notch water quality and that puffers have adequate space and environmental enrichments to prevent stereotypical abrading of eyes on glass surfaces.
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Submitted By: longhairedgit
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