German Shepherd with Pannus

Pannus lesions (darker spots) can be seen on the cornea of this 10-year-old German shepherd. Photo courtesy of Dr. Maria Bates.

Background

Pannus, also called chronic superficial keratitis, is a condition affecting a dog's cornea (the clear outer covering of the eye that is attached to the white sclera). With this disease, blood vessels and scar tissue invade the cornea, and if untreated, it can lead to blindness. While pannus is a lifelong issue, it can usually be managed even though it can’t be completely cured.

This condition is more common in areas with high altitudes, heavy air pollution, or intense UV light exposure, as it's thought to be linked to immune system reactions to irritants like UV rays. Pannus is most often seen in German Shepherds and their mixes but can also affect Greyhounds, Rottweilers, Belgian Shepherds, Belgian Tervurens, Rhodesian Ridgebacks, Siberian Huskies, and other breeds.

Dogs between 5 and 8 years old are most at risk, and the condition tends to be more severe and harder to treat if it shows up in younger dogs.

Signs

• A film spreads across the cornea, and it becomes opaque (white or grey). As time goes by, the cornea can become darkly pigmented and completely opaque, which decreases vision.
• Plasmoma, a thickening of the third eyelid, can occur alongside pannus or it can be seen alone. 
• Third eyelids with plasmoma become inflamed, thickened, and lose the black color along the free (outer) edge. The free edge can also become irregular or scalloped. 
• Both eyes are affected, although one may look worse than the other. Usually, a pinkish film starts at the outer aspect of the cornea and conjunctiva (membrane covering inner eyelids) and spreads towards the center of the eye.
• Pannus and plasmoma are not painful.
• Again, if left untreated, blindness can happen.

Diagnosis

A veterinary eye exam can diagnose pannus.

Treatment

Pannus and plasmoma are not typically curable but can often be controlled. The goal of treatment is to keep the disease from getting worse over time and achieve remission. Flare-ups are common and can occur at various seasons/times of the year.

Depending on the severity of the disease, eye drops and/or ointments may be prescribed several times a day. Generally, a corticosteroid medication is started initially. In severe cases or for plasmoma, cyclosporine, tacrolimus, or pimecrolimus may be added to the steroid.

When a dog is blind or nearly blind from the disease or when the eye does not respond to topical medications, a subconjunctival injection of corticosteroids may be considered. Cyclosporin implants inserted under the conjunctiva have been used successfully in a few eyes with severe disease.

Periodic eye exams (initially in 3-4 weeks, then every 1 to 2 months, and eventually tapered to 3 to 4 times per year) are done to watch for signs of flare-ups so the treatments can be modified before the pannus becomes severe.

Decreasing exposure to UV light may be recommended. Your veterinarian may recommend that your dog be kept inside during hours of peak sunlight and/or be fitted with UV protective goggles.

Prognosis

Most dogs with mild to moderate pannus, especially middle-aged or older dogs with less UV light exposure (live at low altitudes) respond well to topical medications. Dogs that live or work at high altitudes can be much harder to treat.

All dogs with pannus must be carefully monitored for flare-ups with periodic exams as your veterinarian recommends. If your dog is not responding to treatment as expected or is resistant to initial therapy, they may be referred to a veterinary ophthalmologist (eye specialist) for further evaluation and to determine if other treatment options should be considered.