Eye Care for Animals - The Leaders in Veterinary Ophthalmology

Pannus (Chronic Superficial Keratitis)

Pannus (aka chronic superficial keratitis) is a progressive inflammatory disease of the cornea. Common clinical signs include pigmentation (brown discoloration), vascularization (blood vessel ingrowth) and opacification (haziness) of the cornea. These corneal changes may lead to scarring and at worst, blindness. Active disease may result in discomfort

Cause

The cause of pannus is not known, but several factors may be involved:

1. An increased incidence in certain breeds (German Shepherd dog, Labrador Retriever, Border Collie and Greyhound) suggests a genetic predisposition.
2. Ultraviolet radiation increases the severity of the disease Therefore, dogs living at high altitudes and low latitudes often are more severely affected with disease that is more difficult to control. It is most common in the desert southwest and the Rocky Mountain states.
3. Immunological factors are believed to contribute. Pannus is considered a form of an autoimmune disease. Here, the body is directing an inappropriate immune response against the tissues of the cornea itself.
4. Many infectious agents have been incriminated. None have been proven to play a significant role in this disease process.

Signs

The cardinal sign of pannus is vascular or pigment infiltration into the clear cornea, causing whitish, pink or brown discoloration. This typically starts at the outside edge of the clear cornea and extends inward. The blood vessel ingrowth and pigmentation of the cornea may progress across the entire corneal surface and in extreme instances, may result in blindness. Eyelid erosions and a thickened, red third eyelid are occasionally seen.

When acute or progressing, the disease is uncomfortable to the dog. When managed appropriately with medications, the disease normally does not cause irritation.

Diagnosis

A diagnosis of pannus is usually made on the basis of characteristic clinical signs.

Treatment

Despite intensive research efforts, no permanent cure exists. However, in the vast majority of cases, the disease progress can be halted and the condition can be managed long-term, especially if therapy is instituted early in the course of the disease. The two initially occurring components, the inflammatory cell infiltrations and the vessel invasion, usually are reversible with therapy, whereas the scarring and pigment depositions often are irreversible once they have occurred. The goals of therapy are to reverse active vascuarlization and to prevent further progression of the scarring and pigment deposition in the cornea.

There are three categories of therapy:

1. Corticosteroid therapy may be administered by intermittent injections under the mucous membrane of the eye and by continuous application of eye drops or ointments. This is the main line of defense against progression of the disease and most often suffices. However, therapy must be lifelong. Even short periods of interrupted therapy, for example 2 to 4 weeks, may cause severe recurrence with devastating effects on the dog’s vision. Topical immunomodulatory therapy in the form of cyclosporine or tacrolimus ointment or drops may improve the condition.
2. Surgical excision of a superficial layer from the affected area may restore vision in opacified eyes. This is called superficial keratectomy. Unfortunately, the post-operative recurrence rate is high and this method remains a last resort.
3. Beta-irradiation may be used when medication alone proves insufficient.

Potential complications associated with the use of these medications include, but are not limited to, inflammation of the pink tissue (conjunctivitis); corneal ulcerations or rupture corneal scarring, vascularization, or mineralization; inflammation inside the eye (uveitis); high pressure within the eye (glaucoma) retinal detachment or degeneration ocular or orbital pai eyelid rubbing; bleeding inside the eye (hyphema), tearing (epiphora). Some of these complications can lead to blindness.

Your awareness of your pet’s symptoms and compliance with recommendations for medication and recheck examinations help control these potential complications.

If you have any questions regarding pannus, please call Eye Care for Animals.