Pannus -- also called chronic superficial keratitis -- is an eye condition characterized by inflammation of the cornea. While this condition is most common in dogs, it can also affect cats. Without proper treatment, pannus can cause vision impairment and even blindness. Here we will review the causes, symptoms, and treatments of pannus in dogs and cats.
Causes of Pannus in Dogs and Cats
Pannus is an immune-mediated condition, which means that it is the result of an inappropriate immune system response that causes the body to attack certain tissues. In the case of pannus, the immune response occurs in the eye, beginning with the conjunctiva (the pink tissue around the eye and inner eyelids) and ultimately extending to the cornea (the transparent surface of the eye). Both eyes are usually affected, and over time, the inflammation can result in cloudiness, vision impairment, and blindness.
Because certain breeds are particularly predisposed, pannus is most likely an inherited condition. Commonly affected breeds include the German Shepherd, Greyhound, Border Collie, Labrador Retriever, and long-haired Dachshund.
Certain factors can contribute to the development of pannus or exasperate an already existing condition. These factors include exposure to sunlight, ultraviolet rays, smoke, or high altitudes (because of the increased UV exposure).
Symptoms of Pannus in Dogs and Cats
The initial symptom of pannus is a painless pink mass or lesion on the outer edge of one or both of the pet’s corneas. Over time, the mass will flatten, take on a darker color, and spread over the cornea as scar tissue. In severe cases, the tissue will darken or spread to the point of causing vision impairment.
The third eyelid -- a membrane located in the inner corner of your pet’s eye -- may also appear inflamed or swollen.
Diagnosis and Treatment for Pannus
Clinical signs are the basis for most pannus diagnoses. Your veterinarian may also perform certain eye tests, including an intraocular pressure test, corneal staining, and biopsy of the cornea or conjunctiva.
Unfortunately, there is no cure for pannus, and scarring and discoloration typically cannot be reversed. However, certain treatments can work to stop the progression of the disease.
Treatments available for pets affected by pannus include:
- Anti-inflammatory medications -- such as corticosteroids, cyclosporine, and tacrolimus -- administered through injections or topically as eye drops or ointments. These medications are highly successful in suppressing the abnormal immune response and stopping the progression of the disease, but they must be used long-term, often for the remainder of your pet’s life.
- In severe cases, your veterinarian may recommend surgery to superficially remove scarring and pigmentation that is causing vision impairment. This procedure is usually a last resort -- the condition commonly recurs following the operation.
The best bet for your pet is to seek treatment early, since advanced scarring and pigmentation can be difficult or even impossible to reverse. If you ever notice a mass, swelling, or discoloration in your pet’s eye, contact your veterinarian immediately.
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