Pannus, or chronic superficial keratitis, is a slow progressive degenerative disease of the dog's cornea. Pannus leads to brown or pink tissue ingrowth, blood vessel ingrowth and scarring. Pannus leads to a slow loss of vision. This condition is seen predominantly in German Shepherd dogs, but occasionally is seen in other breeds as well.
In this patient, the cornea is scarred diffusely, pigmented (single arrow) and vascularized (double arrow).
In this patient, blood vessels (single arrow) are growing into the cornea. Also, small cholesterol deposits are present (double arrow).
Although many infectious agents have been suggested none have been shown to cause the condition. The actual cause of pannus is not known. Several factors are thought to be involved:
1. The fact that it is commonly seen in German Shepherd dogs suggests a hereditary predisposition.
2. Ultraviolet radiation may play a role as an inciting agent and cause worsening of the condition. Dogs living at high altitudes often are more severely affected.
3. Immune factors are believed to contribute to the severity of this disease. This may be allergic-type reactions against materials from outside the body or against the corneal tissue itself.
Initially, redness, ocular discharge and brown pigment may be seen in the conjunctiva (white tissue of the eye). White infiltrates made up of inflammatory cells then invade the clear cornea. Next blood vessels invade the cornea. Finally pink connective tissue grows into the cornea and later becomes brown. In a small number of cases, two other symptoms may occur either alone or together. A thickening, redness, depigmentation and lumpiness of the third eyelid may occur. This is called a plasmoma. The other condition which may occur is chronic, erosive ulceration of the lower eyelid near the inner and outer corners of the eye. Pannus is uncomfortable to the dog. When treated adequately, your pet can be free of this irritation even though the corneas may not clear up completely.
The clinical findings usually are typical enough for a diagnosis to be made for routine pannus. Ocassionally, a biopsy is needed of the eyelid and third eyelid tissue to rule-out cancer as the cause of the ulceration.
Despite intensive research efforts, no permanent cure exists for pannus. However, in the vast majority of cases, the disease progress can be halted and the problem kept stable. In other cases, pannus may be reversed and the corneas will clear. This is most probable if therapy is instituted early during the disease. The inflammatory cell infiltrate and blood vessel invasion are generally reversible with therapy. The connective tissue infiltration and pigment deposits are often not reversible once they have occurred. There are four types of therapy:
1. Corticosteroid (cortisone) therapy. This is the main line of defense against progression of the disease and in most cases is effective. If the pannus is severe, cortisone may be administered by injections under the white of the eye. In all cases drops containing cortisone must be applied to the eye many times a day. Treatment must be kept up for the rest of the pet¹s life. Even short periods of interrupted treatment, i.e., 2-to-4 weeks, may cause severe relapse with worsening of the patient's vision. The main side-effect of prolonged corticosteroid therapy is the adverse effect on corneal wound healing. Microscopic wounds of the outer layer of the cornea often occur. In a normal eye the cornea heals rapidly. If corticosteroid medications are being applied, minor wounds worsen leading to serious corneal ulceration. The main sign seen in patients with ulceration is pain. Therefore, should any patient on cortisone therapy show signs of pain, such as holding the eye shut or pawing at the eye, it is important that the medication be stopped and the doctor consultedimmediately.
2. Cyclosporine is a new medication in the war on pannus. It does work on pannus and doesn't have the side effects of corticosteroids. Unfortunately, cyclosporine doesn't work as quickly and it is usually necessary to continue it twice daily for the rest of the patient¹s life. Often, we will initially prescribe corticosteroids to be used in addition to the cyclosporine. When used together, greater improvements are seen without the side effects associated with high levels of corticosteroids.
3. Surgery may be used when medication does not completely clear the pannus from the cornea. A 'peeling' of the cornea may be required to restore vision in eyes that are severely scarred and pigmented. Unfortunately, treatment is required following surgery to prevent the pannus from recurring as the cornea heals. This method is only used if medication doesn¹t work.
4. Beta-irradiation may be used when medication and surgery prove insufficient. This will not be recommended unless all else fails.
Pannus can be a frustrating condition that requires life-long treatment. Yet with the correct diagnosis and early treatment, vision can be maintained.
Have any questions on this subject? Contact
Dennis Hacker via E-mail:
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