Pannus, also referred to as chronic superficial keratitis, is a chronic inflammation of the cornea and sometimes the third eyelid of both eyes. It arises as a gray, pink film that spreads across the eyes and eventually decreases the dog's vision. As the lesion progresses, superficial vessels invade the cornea and the cornea becomes opaque. With time the cornea becomes thickened and the surface may become rough and pitted.
The cause of pannus is believed to be an immune-mediated inflammation of the cornea that is made worse by external factors. Exposure to ultraviolet radiation and environmental pollution increases the severity of the condition. Dogs that live in areas of extensive sunlight, especially at high elevations tend to have the worst clinical signs. Pannus is not painful, but advanced cases may lead to blindness.
Pannus occurs only in dogs. Most affected dogs are middle-aged, but the disease can develop in young adult dogs. Pannus occurs predominantly in German shepherd
dogs and German shepherd-cross dogs; it also occurs uncommonly in the greyhound, rottweiler, Belgian tervuren, Border collie, golden retriever
, and Australian shepherd.What to Watch For Pannus usually begins as a somewhat symmetrical fleshy, pink-white film that begins at the lower, outer edges of the cornea of both eyes.
Redness and tearing may be noted.
With time the corneas can pigment and turn dark brown.
White fatty deposits in the adjacent cornea may also develop.
The entire cornea may appear opaque.
Vision may be decreased.
The third eyelid may appear thickened or become pink in color.
The condition is not usually painful unless it is complicated by ulceration of the cornea.
Diagnostic tests are necessary to recognize pannus and to exclude other diseases, such as the following:
Corneal granulation tissue from ocular trauma
Squamous cell carcinoma of the cornea and/or third eyelid
The diagnosis of pannus is almost always made based upon the clinical history and the appearance of the eye. Your veterinarian will usually perform a complete eye exam that includes:
Schirmer tear test to rule out tear deficiency (dry eye)
Fluorescein staining to look for ulceration of the cornea
Thorough examination of the eyelids and adjacent structures of the eye
Your veterinarian may elect to refer your dog to a veterinary ophthalmologist for a comprehensive eye examination, to confirm the diagnosis and to obtain advice on the best therapies to institute.
Pannus is a disease that is controllable, but not usually cured. Treatment of pannus relies on the use of topical corticosteroids and immune-modulating agents such as cyclosporine. In many cases the use of topical drugs can be decreased in frequency as the pannus comes under control, but the drugs cannot usually be stopped entirely. Rarely does the problem completely resolve and the vast majority of cases require lifelong therapy.
Topical corticosteroids are the mainstay of therapy. Medications may include dexamethasone, prednisolone phosphate, betamethasone or prednisolone acetate, which are instituted two to four times daily.
Steroids may be injected under the conjunctiva in severe cases and are given in addition to topical steroids. These injectable steroids include methylprednisolone, triamcinolone, or betamethasone.
Topical cyclosporine 0.2% ointment (Optimmune) is also helpful, particularly in the control of pannus of the third eyelid. Topical cyclosporine is usually used in conjunction with topical steroids, and often allows the frequency of the steroids to be reduced.
For severe cases of pannus that are refractory to the usual treatments, radiation therapy with beta-irradiation may be considered.
Home Care and Prevention
It is important to follow the instructions given to you by your veterinarian. Periodic ocular examination is recommended to evaluate the effectiveness of treatment. Following initiation of therapy, the dog is often rechecked within two to three weeks. Subsequent rechecks are often recommended one month later, three months later and eventually every four months for the rest of the dog's life.
Pannus is typically not preventable, but controlling certain environmental factors can help in the control of the disease. Affected dogs should have limited exposure to bright sunlight. They must also be monitored for seasonal or periodic exacerbations of the disease. Recurrences often develop during warm, sunny weather or at times of significant snow glare.