Pannus, or chronic superficial keratitis is a slowly progressive disease of the canine cornea, characterized by pigmentation, vascularization and opacification. These corneal changes may lead to scarring and at worst, blindness. Additionally, when the disease is active, many patients exhibit signs of discomfort.

Cause
The cause is not known, but several factors are probably involved:

The breed incidence suggests a heritable predisposition as it is seem most commonly in the German Shepherd dog. Other breeds which present frequently include the Laborador Retriever, the Border Collie and the Greyhound.

Ultraviolet radiation plays an important role as an inciting and propagating factor. Therefore, dogs living at high altitudes and low latitudes often are more severely affected. It is most common in the desert southwest and the Rocky Mountain states.

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 corneal substance itself.

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 opacification. This typically starts at the edge of the clear cornea and extends inward. The most common location is at the outer, lower corner of the eye.

Initially, redness and brown pigment may be seen in the mucous membrane just outside the edge of the cornea. Whitish infiltrates of inflammatory cells into the cornea ensues, followed by ingrowth of new blood vessels into the normally avascular cornea. Later, connective tissue grows in and pigments or becomes brownish in time.

In a small number of cases, two other symptoms may occur, simultaneously or one at a time. These are thickening, redness and depigmentation of the third eyelid and chronic, erosive ulcers of the lower eyelid near the inner corner of the eye.

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

Diagnosis
The clinical signs usually are typical enough for a diagnosis to be made, especially when seen in a German Shepherd dog as the disease is most common in this breed.  However, any breed of dog may be affected.

Treatment
Despite intensive research efforts, no permanent cure exists. However, in the vast majority of cases, the disease progress can be halted and the problem kept stable, 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 final connective tissue and pigment depositions often are irreversible once they have occurred.

There are three categories of therapy:
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.

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 kept up consistently for the rest of the dog’s life. Even short periods of interrupted therapy, for example 2 to 4 weeks, may cause severe recurrence with devastating effects on the dog’s vision.

2. Topical immunosuppressive or immunomodulating therapy in the form of cyclosporine or tacrolimus ointment or drops may improve the condition.

3. Excision of a superficial layer from the affected area may restore vision in opacified eyes. This is called superficial keratectomy. However, the recurrence rate postoperatively is high and this method remains only as a last resort.

4. Beta-irradiation may be used when medication alone proves insufficient. However, the recurrence rate postoperatively is high and this method remains only as a last resort.

The medical treatment for Pannus generally includes life-long topical medications designed to slow progression of the disease process and to reverse some of the damage already done. Life-long topical medications seldom give rise to complications, which occur in less than 5% of these cases. Nevertheless, potential complications include, but are not limited to, inflammation of the pink tissue (conjunctivitis); corneal ulcerations (superficial to deep); corneal scarring, vascularization, or mineralization; ocular rupture, secondary to ulceration; inflammation inside the eye (uveitis), secondary to infection or ulceration; high pressure within the eye (glaucoma), secondary to uveitis; retinal detachment or degeneration, secondary to uveitis or infection; ocular or orbital pain, secondary to uveitis, glaucoma or infection; eyelid rubbing; bleeding inside the eye (hyphema), secondary to uveitis or infection; tearing (epiphora); and/or lens luxation, secondary to uveitis, glaucoma or infection. 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 about Pannus (Chronis superficial keratitis), please do not hesitate to call us at Eye Care for Animals.